North Korea reportedly warned Japan that Tokyo would be the first target if Pyongyang decides to play its nuclear card.

The warning reportedly is in response to Tokyo’s standing orders to destroy any missile heading toward Japan, according to Korean Central News Agency. Japan has deployed PAC-3 missile interceptor units around Tokyo to protect its capital and is taking North Korea’s rhetoric seriously.

“We are doing all we can to protect the safety of our nation,” chief Cabinet spokesman Yoshihide Suga said, though he and Ministry of Defense officials refused to confirm the reports about the naval alert, saying they do not want to “show their cards” to North Korea.

Japanese officials long have feared that North Korea not only has the means but several potential motives for launching an attack on Tokyo or major U.S. military installations on Japan’s main island.

“If Kim Jong Un decides to launch a missile, whether it’s across the Sea of Japan or some other direction, he will be choosing willfully to ignore the entire international community,” U.S. Secretary of State John Kerry told reporters in South Korea. “And it will be a provocation and unwanted act that will raise people’s temperatures.”

“We will stand with South Korea and Japan against these threats. And we will defend ourselves,” he said.

Kerry also weighed in on an intelligence report that rocked Washington on Thursday and suggested that North Korea now had the knowhow to arm a ballistic missile with a nuclear warhead — even if the weapons would lack reliability. Citing the Pentagon’s assessment, Kerry rejected the finding and said that Pyongyang still hadn’t developed or fully tested the nuclear capacities needed for such a step.

Speaking beside Kerry, South Korea Foreign Minister Yun Byung-se called for more United Nations action against Pyongyang if it commits another provocation.

He refused to comment specifically on the U.S. intelligence report, saying only that the North has “high nuclear and missile capabilities” but that it is still some time away from a nuclear bomb that is “small, light and diversified.”

Kerry offered strong words of solidarity for South Korea, and praised South Korea President Park Geun-hye’s “bright vision” of a prosperous and reunified Korean Peninsula without nuclear weapons. By contrast, he said North Korea’s Kim,  has a choice to make between provocation and returning to talks to de-escalate tension and lead to the end of its nuclear program

Both Yun and Kerry kept the door open for future negotiations with Pyongyang.

But both seemed to suggest that they were unlikely in light of the North’s increasingly bombastic threats, including nuclear strikes on the United States. Most experts say those are unfeasible based on the North’s current capacity and would never be explored seriously because the U.S. response would be overwhelming against a regime focused primarily on survival.

Kerry said any talks with North Korea have to lead toward denuclearization.

They have to be really serious,” Kerry said. “No one is going to talk for the sake of talking and no one is going to play this round-robin game that gets repeated every few years, which is both unnecessary and dangerous.”

Published April 12, 2013 / FoxNews.com /The Associated Press contributed to this report.

Obama administration officials scrambled to downplay the errant disclosure of a classified portion of an intelligence report finding that North Korea has advanced its nuclear knowledge to the point that it could arm a ballistic missile with a nuclear warhead.

The analysis, disclosed Thursday at a hearing on Capitol Hill, says the Pentagon’s intelligence wing has “moderate confidence” that North Korea has nuclear weapons capable of delivery by ballistic missiles but that the weapon was unreliable.

The revelation was significant, because it has not been previously reported or believed that the country had the ability to miniaturize and deliver a nuclear weapon.

But top U.S. officials repeatedly stressed that the finding does not mean North Korea has the capabilities to launch a nuclear missile with any reliability at this point.

“It is inaccurate to suggest that the (North Korea) has the capability articulated in that report — they have a missile but that is very different than having the militarization, nuclearization, etcetera,” Secretary of State John Kerry said Friday, after landing in South Korea as part of a tour of Asian countries.

On Thursday night, the Pentagon and Director of National Intelligence James Clapper both downplayed the report.

“While I cannot speak to all the details of a report that is classified in its entirety, it would be inaccurate to suggest that the North Korean regime has fully tested, developed, or demonstrated the kinds of nuclear capabilities referenced in the passage,” Pentagon spokesman George Little said. Clapper echoed the assessment.

Meanwhile, North Korea was leveling new threats Friday. According to South Korea’s Yonhap News Agency, the regime warned that Tokyo would, in the event of a war, be the first target “if it continues to maintain its hostile posture.” North Korea was apparently threatening Japan because it vowed to destroy any missile heading toward the country.

Separately, South Korean President Park Geun-hye reportedly said she’s open to working with the North to resolve the standoff if the regime ends its provocative behavior.

The dispute over the North’s nuclear capability started with the Capitol Hill hearing Thursday. At the hearing, Rep. Doug Lamborn, R-Colo., read aloud what he said was an unclassified paragraph from a secret Defense Intelligence Agency report that was supplied to some members of Congress.

He said, reading from the report: “DIA assesses with moderate confidence the North currently has nuclear weapons capable of delivering by ballistic missiles, however the reliability will be low.”

The reading seemed to take Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, by surprise, who said he hadn’t seen the report and declined to answer questions about it.

Pentagon officials told Fox News that the memo he read from was in fact classified. However, someone at the Defense Intelligence Agency mistakenly marked it “unclassified,” which led to the confusion.

A U.S. official in Seoul said Friday it is “premature” to say North Korea has developed the expertise to make a nuclear weapon small enough to put on a ballistic missile.

“It is a very difficult task,” the official told Fox News. “They haven’t been able to put everything together.”

The official also says there is no indication a North Korea missile launch is imminent, saying officials “have not seen activity” that would show that a launch will happen soon, or that the country is planning a large scale attack.

“There has been no indication of massive troop movements or anything to back up the rhetoric going on,” the official said.

Meanwhile, Kerry’s trip to South Korea comes in the midst of bellicose threats from the unpredictable communist regime in the North.

Kerry and his South Korean counterpart said in a joint press conference Friday that North Korea will gain nothing by threatening tests of its missile or nuclear programs.

Kerry said the U.S. and its Asian ally won’t accept the North as a nuclear power, calling the country’s rhetoric “unacceptable.”

South Korean Foreign Minister Yun Byung-se called Pyongyang’s threats a “grave provocation” to the entire international community.

Since the beginning of March, the Navy has moved two missile defense ships closer to the coast of the Korean peninsula, in part to protect against a potential missile launch aimed at Guam, a U.S. territory in the Pacific.

The Pentagon also has announced it will place a more advanced land-based missile defense on Guam, and Hagel said in March that he approved installing 14 additional missile interceptors in Alaska to bolster a portion of the missile defense network that is designed to protect all of U.S. territory.

On Thursday, the Pentagon said it had moved a sea-based X-band radar — designed to track warheads in flight — into position in the Pacific.

Notably absent from that unclassified segment of the Pentagon report was any reference to what the DIA believes is the range of a missile North Korea could arm with a nuclear warhead. Much of its missile arsenal is capable of reaching South Korea and Japan, but Kim has threatened to attack the United States as well.

But David Wright, a nuclear weapons expert at the Union of Concerned Scientists, said the DIA assessment probably does not change the views of those who closely follow developments in North Korea’s pursuit of a nuclear weapon.

“People are starting to believe North Korea very likely has the capability to build a nuclear weapon small enough to put on some of their shorter-range missiles,” Wright said. “Once you start talking about warheads small enough and technically capable to be on a long-range missile, I think it’s much more an open question.”

The DIA assessment is not out of line with comments Dempsey made Wednesday when he was asked at a Pentagon news conference whether North Korea was capable of pairing a nuclear warhead to a ballistic missile that could reach Japan or beyond.

In response, Dempsey said the extent of North Korean progress on designing a nuclear weapon small enough to operate as a missile warhead was a classified matter. But he did not rule out that the North has achieved the capability revealed in the DIA report.

“They have conducted two nuclear tests,” Dempsey told a Pentagon news conference. “They have conducted several successful ballistic missile launches. And in the absence of concrete evidence to the contrary, we have to assume the worst case, and that’s why we’re postured as we are today.” He was referring to recent moves by the U.S. to increase its missile defense capabilities in the Pacific.

At the same House hearing where Lamborn revealed the DIA conclusion, Defense Secretary Chuck Hagel was asked a different version of the same question: Does North Korea have the capability to strike U.S. territory with a nuclear weapon? Hagel said the answer is no.

“Now does that mean that they won’t have it or they can’t have it or they’re not working on it?” Hagel added. “No. That’s why this is a very dangerous situation.”

“Now is the time for North Korea to end the belligerent approach they have taken and to try to lower temperatures,” Obama said in his first public comments since Pyongyang threatened the United States and its allies in East Asia with nuclear attack.

Obama, speaking from the Oval Office, said he preferred to see the tensions on the peninsula resolved through diplomatic means, but added that “the United States will take all necessary steps to protect its people.”

The North on Thursday delivered a fresh round of war rhetoric with claims it has “powerful striking means” on standby, the latest in a torrent of warlike threats seen by outsiders as an effort to scare and pressure South Korea and the U.S. into changing their North Korea policies.

Fox News’ Justin Fishel and Greg Palkot and The Associated Press contributed to this report.

Former British Prime Minister Margaret Thatcher has died after suffering a stroke at the age of 87. Known as ‘The Iron Lady,’ Thatcher was Britain’s only female prime minister and led the Conservatives to three election victories, governing from 1979 to 1990.

The U.K. press is reporting that Thatcher suffered a stroke and her children said in a statement she passed “peacefully.”

“It is with great sadness that Mark and Carol Thatcher announced that their mother Baroness Thatcher died peacefully following a stroke this morning,” Lord Bell, Thatcher’s spokesperson, said.

Thatcher, known as the “Iron Lady,” was a staunch critic of Communism and delivered several memorable lines while defending Capitalism. For example, during her last speech in the House of Commons in 1990, she delivered a rousing rebuttal to a member of Parliament who questioned her policies and their affect on the poor.

The U.K. press is reporting that Thatcher suffered a stroke and her children said in a statement she passed “peacefully.”

“It is with great sadness that Mark and Carol Thatcher announced that their mother Baroness Thatcher died peacefully following a stroke this morning,” Lord Bell, Thatcher’s spokesperson, said.

Thatcher, known as the “Iron Lady,” was a staunch critic of Communism and delivered several memorable lines while defending Capitalism. For example, during her last speech in the House of Commons in 1990, she delivered a rousing rebuttal to a member of Parliament who questioned her policies and their affect on the poor.

She ruled for 11 remarkable years and imposed her will on a fractious, rundown nation – breaking the unions, triumphing in a far-off war, and selling off state industries at a record pace. She left behind a leaner government and more prosperous nation by the time a mutiny ousted her from No. 10 Downing Street.

For admirers, Thatcher was a savior who rescued Britain from ruin and laid the groundwork for an extraordinary economic renaissance. For critics, she was a heartless tyrant who ushered in an era of greed that kicked the weak out onto the streets and let the rich become filthy rich.

“Let us not kid ourselves, she was a very divisive figure,” said Bernard Ingham, Thatcher’s press secretary for her entire term. “She was a real toughie. She was a patriot with a great love for this country, and she raised the standing of Britain abroad.”

Thatcher was the first – and still only – female prime minister in Britain’s history. But she often found feminists tiresome and was not above using her handbag as a prop to underline her swagger and power. A grocer’s daughter, she rose to the top of Britain’s snobbish hierarchy the hard way, and envisioned a classless society that rewarded hard work and determination.

She was a trailblazer who at first believed trailblazing impossible: Thatcher told the Liverpool Daily Post in 1974 that she did not think a woman would serve as party leader or prime minister during her lifetime.

But once in power, she never showed an ounce of doubt.

Thatcher could be intimidating to those working for her: British diplomats sighed with relief on her first official visit to Washington, D.C., as prime minister to find that she was relaxed enough to enjoy a glass of whiskey and a half-glass of wine during an embassy lunch, according to official documents.

Like her close friend and political ally Ronald Reagan, Thatcher seemed motivated by an unshakable belief that free markets would build a better country than reliance on a strong, central government. Another thing she shared with the American president: a tendency to reduce problems to their basics, choose a path, and follow it to the end, no matter what the opposition.

She formed a deep attachment to the man she called “Ronnie” – some spoke of it as a schoolgirl crush. Still, she would not back down when she disagreed with him on important matters, even though the United States was the richer and vastly stronger partner in the so-called “special relationship.”

Thatcher was at her brashest when Britain was challenged. When Argentina’s military junta seized the remote Falklands Islands from Britain in 1982, she did not hesitate even though her senior military advisers said it might not be feasible to reclaim the islands.

She simply would not allow Britain to be pushed around, particularly by military dictators, said Ingham, who recalls the Falklands War as the tensest period of Thatcher’s three terms in power. When diplomacy failed, she dispatched a military task force that accomplished her goal, despite the naysayers.

“That required enormous leadership,” Ingham said. “This was a formidable undertaking, this was a risk with a capital R-I-S-K, and she demonstrated her leadership by saying she would give the military their marching orders and let them get on with it.”

Thatcher served from 1979-1990.

This is a breaking story. Updates will be added. ​The Associated Press contributed to this report.

As tensions continued to mount on the Korean peninsula, the communist dictatorship in the North deployed mid-range missile launchers to its east coast and reportedly warned foreign embassies Friday it cannot guarantee the safety of diplomats after April 10.

Reuters reported early Friday that North Korea deployed two of its intermediate range missiles on mobile launchers and hid them on the east coast of the country, citing a South Korean news agency.

South Korea said Thursday North Korea moved a missile with “considerable range” to its east coast after an unnamed spokesman for the North Korean army warned the U.S. Wednesday that its military has been cleared to wage an attack using “smaller, lighter and diversified nuclear” weapons.

Meanwhile, the United Kingdom foreign office confirmed in a statement Friday that North Korea asked a number of foreign embassies in Pyongyang  to consider moving staff out since they could not assure their safety in the event of conflict.

“We are consulting international partners about these developments.  No decisions have been taken, and we have no immediate plans to withdraw our Embassy,”  the UK foreign office statement said.

Under the Vienna Convention that governs diplomatic missions, host governments are required to assist in the evacuation of embassy staff from the country in the event of conflict.

North Korea has railed for weeks against joint U.S. and South Korean military exercises taking place in South Korea and has expressed anger over tightened sanctions for a February nuclear test.

“The current question was not whether, but when a war would break out on the peninsula,” because of the “increasing threat from the United States”, China’s state news agency Xinhua quoted the North’s Foreign Ministry as saying, according to a Reuters report.

U.S. National Security Council spokesperson Caitlin Hayden has called North Korea’s threats “unhelpful and unconstructive.”

“It is yet another offering in a long line of provocative statements that only serve to further isolate North Korea from the rest of the international community and undermine its goal of economic development,” she said. “North Korea should stop its provocative threats and instead concentrate on abiding by its international obligations.”

South Korean Defense Minister Kim Kwan-jin dismissed reports in the Japanese and South Korean media that the missile moved this week could be a KN-08, which is believed to be a long-range missile that if operable could hit the United States.

Kim told lawmakers at a hearing that the missile’s range is considerable but not far enough to hit the U.S. mainland. He said he did not know the reasons behind the missile movement, saying it “could be for testing or drills.”

The range he described could refer to a mobile North Korean missile known as the Musudan, which has a range of 1,800 miles. That would make Japan and South Korea potential targets, but little is known about the missile’s accuracy.

Despite North Korea’s rhetoric, analysts say they do not expect a nuclear attack, which knows the move could trigger a destructive, suicidal war that no one in the region wants.

“The rhetoric is off the charts,” said Victor Cha, former director for Asian affairs at the White House National Security.

Following through on one threat Wednesday, North Korean border authorities refused to allow entry to South Koreans who manage jointly run factories in the North Korean city of Kaesong.

Washington calls the military drills, which this time have incorporated fighter jets and nuclear-capable stealth bombers, routine annual exercises between the allies. Pyongyang calls them rehearsals for a northward invasion.

South Korea says North Korea has moved a missile with “considerable range” to its east coast after an unnamed spokesman for the North Korean army warned the U.S. Wednesday that its military has been cleared to wage an attack using “smaller, lighter and diversified nuclear” weapons.

South Korea’s defense minister said Thursday the missile moved is not capable of hitting the United States.

Kim Kwan-jin dismissed reports in Japanese and South Korean media that the missile could be a KN-08, which is believed to be a long-range missile that if operable could hit the United States.

Kim told lawmakers at a hearing that the missile’s range is considerable but not far enough to hit the U.S. mainland. He said he did not know the reasons behind the missile movement, saying it “could be for testing or drills.”

The range he described could refer to a mobile North Korean missile known as the Musudan, which has a range of 1,800 miles. That would make Japan and South Korea potential targets, but little is known about the missile’s accuracy.

North Korea has railed for weeks against joint U.S. and South Korean military exercises taking place in South Korea and has expressed anger over tightened sanctions for a February nuclear test.

The army spokesman said in a statement carried by the Korean Central News Agency that troops have been authorized to counter U.S. aggression with “powerful practical military counteractions.”

National Security Council spokesperson Caitlin Hayden called the threats “unhelpful and unconstructive.”

“It is yet another offering in a long line of provocative statements that only serve to further isolate North Korea from the rest of the international community and undermine its goal of economic development,” she said. “North Korea should stop its provocative threats and instead concentrate on abiding by its international obligations.”

The Pentagon said in Washington that it will deploy a missile defense system to the U.S. Pacific territory of Guam to strengthen regional protection against a possible attack from North Korea. The defense secretary said the U.S. was seeking to defuse the situation.

Despite the rhetoric, analysts say they do not expect a nuclear attack by North Korea, which knows the move could trigger a destructive, suicidal war that no one in the region wants.

The strident warning from Pyongyang is latest in a series of escalating threats from North Korea, which has railed for weeks against joint U.S. and South Korean military exercises taking place in South Korea and has expressed anger over tightened sanctions for a February nuclear test.

Following through on one threat Wednesday, North Korean border authorities refused to allow entry to South Koreans who manage jointly run factories in the North Korean city of Kaesong.

Washington calls the military drills, which this time have incorporated fighter jets and nuclear-capable stealth bombers, routine annual exercises between the allies. Pyongyang calls them rehearsals for a northward invasion.

The foes fought on opposite sides of the three-year Korean War, which ended in a truce in 1953. The divided Korean Peninsula remains in a technical state of war six decades later, and Washington keeps 28,500 troops in South Korea to protect its ally.

U.S. Defense Secretary Chuck Hagel said Washington was doing all it can to defuse the situation, echoing comments a day earlier by Secretary of State John Kerry.

“Some of the actions they’ve taken over the last few weeks present a real and clear danger and threat to the interests, certainly of our allies, starting with South Korea and Japan and also the threats that the North Koreans have leveled directly at the United States regarding our base in Guam, threatened Hawaii, threatened the West Coast of the United States,” Hagel said Wednesday.

In Pyongyang, the military statement said North Korean troops had been authorized to counter U.S. “aggression” with “powerful practical military counteractions,” including nuclear weapons.

“We formally inform the White House and Pentagon that the ever-escalating U.S. hostile policy toward the DPRK and its reckless nuclear threat will be smashed by the strong will of all the united service personnel and people and cutting-edge smaller, lighter and diversified nuclear strike means,” an unnamed spokesman from the General Bureau of the Korean People’s Army said in a statement carried by state media, referring to North Korea by its formal name, the Democratic People’s Republic of Korea. “The U.S. had better ponder over the prevailing grave situation.”

However, North Korea’s nuclear strike capabilities remain unclear.

Pyongyang is believed to be working toward building an atomic bomb small enough to mount on a long-range missile. Long-range rocket launches designed to send satellites into space in 2009 and 2012 were widely considered covert tests of missile technology, and North Korea has conducted three underground nuclear tests, most recently in February.

“I don’t believe North Korea has to capacity to attack the United States with nuclear weapons mounted on missiles, and won’t for many years. Its ability to target and strike South Korea is also very limited,” nuclear scientist Siegfried Hecker, a senior fellow at the Center for International Security and Cooperation at Stanford University, said this week.

“And even if Pyongyang had the technical means, why would the regime want to launch a nuclear attack when it fully knows that any use of nuclear weapons would result in a devastating military response and would spell the end of the regime? ” he said in answers posted to CISAC’s website.

In Seoul, a senior government official said Tuesday that it wasn’t clear how advanced North Korea’s nuclear weapons capabilities are. But he also noted fallout from any nuclear strike on Seoul or beyond would threaten Pyongyang as well, making a strike unlikely. He spoke on condition of anonymity because he wasn’t authorized to speak publicly to the media.

North Korea maintains that it needs to build nuclear weapons to defend itself against the United States. On Monday, North Korean leader Kim Jong Un led a high-level meeting of party officials who declared building the economy and “nuclear armed forces” as the nation’s two top priorities.

The Associated Press contributed to this report.

Defense Secretary Chuck Hagel said Wednesday that North Korea’s rising threats pose a “real and clear danger,” as the Pentagon continued to take precautions with a plan to deploy a missile-defense system to Guam.

A senior U.S. official confirmed to Fox News that the military will deploy an Army system shown as a Terminal High Altitude Area Defense battery to Guam. The system is capable of shooting down short-, medium- and intermediate-range ballistic missiles.

This follows the positioning of two U.S. destroyer ships in the region, along with plans to have two sea-based radar systems in the western Pacific.

At the same time, North Korea seemed to ramp up its rhetoric even further Wednesday, warning that it’s military had been cleared to attack the U.S. with “smaller, lighter and diversified nuclear” weapons. The National Security Council responded by saying such “unhelpful and unconstructive threats … only serve to further isolate North Korea.”

Hagel, speaking Wednesday at the National Defense University, said the cascade of threats out of North Korea must be taken “seriously,” given the country’s nuclear and missile-delivery capacity — though analysts say the country still could not fire a nuclear-tipped missile all the way to the continental United States.

“As they have ratcheted up (their) bellicose, dangerous rhetoric — and some of the actions they’ve taken over the last few weeks present a real and clear danger and threat to the interests, certainly of our allies, starting with South Korea and Japan,” Hagel said. He also cited the “threats that the North Koreans have leveled directly at the United States regarding our base in Guam, threatened Hawaii, threatened to the West Coast of the United States.”

The Kim Jong Un regime has toggled in recent weeks between threatening the U.S. and threatening South Korea.

In addition to announcing through an unnamed army spokesman that it had cleared a strike plan for a potential attack on the U.S., North Korea said Wednesday it had decided to bar South Korean managers and trucks delivering supplies from crossing the border to enter a jointly run factory park called Kaesong.

The Kaesong industrial park started producing goods in 2004 and has been an unusual point of cooperation in an otherwise hostile relationship between the Koreas, whose three-year war ended in 1953 with an armistice, not a peace treaty.

The Kaesong move came a day after the North said it would restart its long-shuttered plutonium reactor and a uranium enrichment plant. Both could produce fuel for nuclear weapons that North Korea is developing and has threatened to hurl at the U.S., something experts don’t think it will be able to accomplish for years.

The North’s rising rhetoric has been met by a display of U.S. military strength, including flights of nuclear-capable bombers and stealth jets at annual South Korean-U.S. military drills that the allies call routine and North Korea says are invasion preparations.

In a telephone call Tuesday evening to Chinese Defense Minister Chang Wanquan, Hagel cited North Korea’s pursuit of nuclear weapons and ballistic missiles and said Washington and Beijing should continue to cooperate on those problems.

“The secretary emphasized the growing threat to the U.S. and our allies posed by North Korea’s aggressive pursuit of nuclear weapons and ballistic missile programs and expressed to General Chang the importance of sustained U.S.-China dialogue and cooperation on these issues,” Pentagon spokesman George Little said in a statement describing the phone call.

Little also disclosed that Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, will visit China later this month. It would be Dempsey’s first trip to China as head of the Joint Chiefs.

Hagel also invited the Chinese defense minister to visit the United States this year.

Fox News’ Justin Fishel and The Associated Press contributed to this report.

PAJU, South Korea –  North Korea on Wednesday barred South Korean workers from entering a jointly run factory park just over the heavily armed border in the North in the latest sign that Pyongyang’s warlike stance toward South Korea and the United States is moving from words to action.

The Kaesong move came a day after the North announced it would restart its long-shuttered plutonium reactor and a uranium enrichment plant, both of which could produce fuel for nuclear weapons that Pyongyang is developing and has threatened to hurl at the U.S. but which experts don’t think it will be able to accomplish for years.

The North’s rising rhetoric over recent weeks has been met by a display of U.S. military strength, including flights of nuclear-capable bombers and stealth jets at the annual South Korean-U.S. military drills that the allies call routine but that North Korea claims are invasion preparations.

The Kaesong industrial park started producing goods in 2004 and has been an unusual point of cooperation in an otherwise hostile relationship between the Koreas, whose three-year war ended in 1953 with an armistice. Its continued operation even through past episodes of high tension has reassured foreign multinationals that another Korean War is unlikely and their investments in prosperous dynamic South Korea are safe.

“The Kaesong factory park has been the last stronghold of detente between the Koreas,” said Hong Soon-jik, a North Korea researcher at the Seoul-based Hyundai Research Institute.

He said tension between the Koreas could escalate further over Kaesong because Seoul may react with its own punitive response and Pyongyang will then hit back with another move.

It is unclear how long North Korea will prevent South Koreans from entering the industrial park, which is located in the North Korean border city of Kaesong and provides jobs for more than 50,000 North Koreans. The last major disruption at the park amid tensions over U.S.-South Korean military drills in 2009 lasted just three days.

Seoul’s Unification Ministry spokesman Kim Hyung-suk said Pyongyang was allowing South Koreans to return home from Kaesong. Some 33 workers of about 860 South Koreans at Kaesong returned Wednesday. But Kim said about 480 South Koreans who had planned to travel to the park Wednesday were being refused entry.

Trucks streamed back into South Korea through its Paju border checkpoint in the morning, just minutes after heading through it, after being refused entry into the North.

Pyongyang threatened last week to shut down the park, which is run with North Korean labor and South Korean know-how. It expressed anger over South Korean media reports that said North Korea hadn’t yet shut the park because it is a source of crucial hard currency for the impoverished country.

About 120 South Korean companies operate factories in Kaesong which produced $470 million of goods such as clocks, clothing and shoes last year that are trucked back to the South for export to other countries. The industrial park is crucial for the small businesses that operate there to take advantage of North Korea’s low wages but not important for the South Korean economy overall.

It has more significance to cash-strapped North Korea since, according to the South Korean government, wages for North Korean workers totaled some $81 million last year. That has underlined the risks that North Korea’s brinkmanship will result in a miscalculation that results in an even more dangerous polarization of the Korean peninsula.

Barring entry to South Koreas is a “slap in the face” after the South Korean government recently extended medical aid to the North, said Lee Choon-kun, a North Korea researcher at the Korea Economic Research Institute, a Seoul-based think tank. “I see this as a start for more provocative actions,” he said.

“The North has made too many threats not to stop short of any real action.”

Kaesong, initially conceived as a test case for reunification and reconciliation, also provides an irksome reminder for Pyongyang that what it lacks, the South has in abundance — material prosperity. An enormous gap emerged between the two Koreas in the decades after the Korean War as the South embraced a form of state-directed capitalism while the North adhered to communist central planning.

Every morning, North Korean workers commute to the complex on the edge of Kaesong on South Korean-made Hyundai buses. Once inside the gates of the complex, it’s a world apart. The paved streets and sidewalks are marked with South Korean traffic signals and signs and the parking lots are filled with the Hyundai, Samsung and KIA cars driven by South Korean managers.

Inside several factories visited by The Associated Press last year, the posters on the walls are not party slogans but safety warnings. “Beware of fires,” read one; “Wash your hands” read another. While most factories in North Korea are drafty, and few have running water, the facilities in Kaesong are equipped with hot water, flush toilets and air conditioners.

In the rest of the Korean Peninsula, it is illegal for Koreans from North and South to interact without government permission. But inside Kaesong, North Korean workers work side by side with South Korean managers, discussing orders and mapping out production.

However, they tend not to socialize with one another. At most factories, North Korean workers take their meals in cafeterias that serve basic stews and rice while the South Koreans dine separately.

Park Yun-kyu, who heads a men’s apparel maker that employs 700 North Korean workers in Kaesong, said he was worried he couldn’t send fresh food to his eight South Korean workers in Kaesong.

“They were working normally when I called them in the morning,” said Park who returned to Seoul after being refused entry into Kaesong. “The problem is food. I hope North Korea would at least let us send food. We have to send food and some materials for production every day.”

On Tuesday, a senior South Korean government official said Seoul has a contingency plan for its citizens in Kaesong. But he said the government hoped the tension would not lead to a shutdown of the complex. He spoke on condition of anonymity, saying he was not authorized to speak publicly to the media.

WASHINGTON –  Defense Secretary Chuck Hagel said Tuesday that North Korea’s development of nuclear weapons poses a “growing threat” to the U.S. and its allies.

In a telephone call Tuesday evening to Chinese Defense Minister Chang Wanquan, Hagel cited North Korea’s pursuit of nuclear weapons and ballistic missiles and said Washington and Beijing should continue to cooperate on those problems.

“The secretary emphasized the growing threat to the U.S. and our allies posed by North Korea’s aggressive pursuit of nuclear weapons and ballistic missile programs and expressed to General Chang the importance of sustained U.S.-China dialogue and cooperation on these issues,” Pentagon spokesman George Little said in a statement describing the phone call.

Little also disclosed that Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, will visit China later this month. It would be Dempsey’s first trip to China as head of the Joint Chiefs.

Hagel also invited the Chinese defense minister to visit the United States this year.

North Korea on Wednesday barred South Korean workers from entering a jointly run factory park just over the heavily armed border in the North, officials in Seoul said, a day after Pyongyang announced it would restart its long-shuttered plutonium reactor and increase production of nuclear weapons material.

Seoul’s Unification Ministry spokesman Kim Hyung-suk said Pyongyang is allowing South Koreans to return home from Kaesong, but that about 480 South Koreans who had planned to travel to the park Wednesday were being refused entry.

North Korean authorities cited recent political circumstances on the Korean Peninsula when they delivered their decision to block South Korean workers from entering Kaesong, Kim said without elaborating.

The two sides do not allow their citizens to travel to the other country without approval, but an exception has previously been made each day for the South Koreans working at Kaesong.

Meanwhile, the Pentagon on Tuesday confirmed that it is positioning an array of military assets near the Korean Peninsula, as the White House stressed that the “entire national security team” is focused on the escalating threats out of Pyongyang — with the latest being a pledge to restart its plutonium reactor.

Secretary of State John Kerry, speaking Tuesday at a news conference with the visiting foreign minister of South Korea, said recent belligerent rhetoric from North Korea is “unacceptable” and that the U.S. will defend itself, as well as South Korea and Japan, from any threat from the North.

The declaration of a resumption of plutonium production — the most common fuel in nuclear weapons — and other facilities at the main Nyongbyon nuclear complex will boost fears in Washington and among its allies about North Korea’s timetable for building a nuclear-tipped missile that can reach the mainland U.S., technology it is not currently believed to have.

The amount of hostile language from North Korea in recent weeks was “extraordinary,” Kerry said, adding that the isolated state should have no doubt that the U.S. will fulfill its treaty obligations to allies in the region.

Pentagon spokesman George Little said that two destroyer warships, the USS Decatur and USS McCain, have arrived in the region as part of a missile-defense mission. Previously, the Pentagon had only revealed that it had moved the USS McCain to the region.

“They have arrived at predetermined positions in the western Pacific, where they will be poised to respond to any missile threats to our allies or our territory,” Little said Tuesday.

In addition, the Pentagon has already announced plans to have two sea-based radar systems in the western Pacific. One is already in northern Japan; the other has not yet deployed and is currently conducting non-North Korean related systems tests off Pearl Harbor.

The system in Japan can serve to protect the Korean peninsula as well as threats to the western United States that originate from North Korea.

Published April 03, 2013 / FoxNews.com /The Associated Press contributed to this report.