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.

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.

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.

A spokesman for the North’s General Department of Atomic Energy said that scientists will begin work at a uranium enrichment plant and a graphite-moderated 5 megawatt reactor, which generates spent fuel rods laced with plutonium and is the core of the Nyongbyon nuclear complex.

The unidentified spokesman said the measure is part of efforts to resolve the country’s acute electricity shortage but also for “bolstering up the nuclear armed force both in quality and quantity,” according to a statement carried by the official Korean Central News Agency.

Pyongyang conducted its third nuclear test in February, prompting a new round of U.N. sanctions that have infuriated its leaders and led to a torrent of threatening rhetoric. The United States has sent nuclear-capable bombers and stealth jets to participate in annual South Korean-U.S. military drills that the allies call routine but that Pyongyang claims are invasion preparations.

North Korea has declared that the armistice ending the Korean War in 1953 is void, threatened to launch nuclear and rocket strikes on the United States and, most recently, declared at a high-level government assembly that making nuclear arms and a stronger economy are the nation’s top priorities.

The threats are seen as efforts to force policy changes in Seoul and Washington and increase domestic loyalty to young North Korean leader Kim Jong Un by portraying him as a powerful military force.

“North Korea is keeping tension and crisis alive to raise stakes ahead of possible future talks with the United States,” said Hwang Jihwan, a North Korea expert at the University of Seoul. “North Korea is asking the world, `What are you going to do about this?”‘

North Korea added the 5-megawatt, graphite-moderated reactor to its nuclear complex at Nyongbyon in 1986 after seven years of construction. The country began building a 50-megawatt and a 200 megawatt reactor in 1984, but construction was suspended under a 1994 nuclear deal with Washington.

North Korea says the facility is aimed at generating electricity. It takes about 8,000 fuel rods to run the reactor. Reprocessing the spent fuel rods after a year of reactor operation could yield about 7 kilograms of plutonium — enough to make at least one nuclear bomb, experts say.

Nuclear bombs can be produced with highly enriched uranium or with plutonium. North Korea is believed to have exploded plutonium devices in its first two nuclear tests, in 2006 and 2009.

In 2010, the North unveiled a long-suspected uranium enrichment program, which would give it another potential route to make bomb fuel. Uranium worries outsiders because the technology needed to make highly enriched uranium bombs is much easier to hide than huge plutonium facilities.

But experts say plutonium is considered better for building small warheads, which North Korea needs if it is going to put them on missiles. Analysts say they don’t believe North Korea currently has mastered such miniaturization technology.

Scientist and nuclear expert Siegfried Hecker has estimated that Pyongyang has 24 to 42 kilograms of plutonium — enough for perhaps four to eight rudimentary bombs similar to the plutonium weapon used on Nagasaki in World War II.

It’s not known whether the North’s latest atomic test, in February, used highly enriched uranium or plutonium stockpiles. South Korea and other countries have so far failed to detect radioactive elements that may have leaked from the test and which could determine what kind of device was used.

“North Korea is dispelling any remaining uncertainties about its intention for developing nuclear arms. It is making it clear that its nuclear arms program is the essence of its national security and that it’s not negotiable,” said Sohn Yong-woo, a professor at the Graduate School of National Defense Strategy of Hannam University in South Korea.

“North Korea is more confident about itself than ever after the third nuclear test,” Sohn said. “That confidence is driving the leadership toward more aggressive nuclear development.”

A U.S. defense official confirmed to Fox News that the Navy had moved the U.S. destroyer to a location near South Korea. The ship, the USS McCain, is equipped with the Aegis defense system and is capable of shooting down missiles. Officials initially misidentified the ship but later clarified the USS McCain had been dispatched.

The defense official said the decision is not part of the ongoing joint military exercise with South Korea but part of the Navy’s general movements. The Navy had the same type of ship in this location as recently as December.

But, the positioning comes after the Pentagon dispatched two F-22 stealth fighter jets to South Korea to join Seoul forces in a training exercise, and after other demonstrations of U.S. capability last week.

White House Press Secretary Jay Carney said Monday that Kim Jong Un’s steadily escalating threats follow a “pattern,” but one that must be taken seriously. He said the U.S. is now taking “prudent” measures to “reassure our allies, demonstrate our resolve to the North and reduce pressure on Seoul to take unilateral action.”

This would include efforts to boost missile defense, last week’s rare flight of B-2 bombers to South Korea and likely the decision Sunday to deploy F-22 Raptors to Osan Air Base in South Korea.

With analysts warning that the biggest threat from North Korea is that it could start a war by going too far and provoking South Korea, Carney suggested the shows of strength are aimed at deterring the North from crossing that line.

“We believe this has reduced the chance of miscalculation and provocation,” Carney said of the B-2 flights and other actions.

Carney, though, said that despite the “harsh rhetoric” out of Pyongyang, the U.S. is not seeing changes to the country’s “military posture,” such as any “large-scale” mobilizations or positioning of forces.

“This pattern of bellicose rhetoric is not new, it is familiar,” Carney said. “We take it very seriously, we take prudent measures in response to it.”

The F-22 flight came after North Korea warned that the Korean Peninsula had entered “a state of war.”

A Pentagon spokesman confirmed to Fox News that the F-22 Raptors were deployed to Osan Air Base in South Korea from Japan on Sunday to support ongoing U.S.-South Korean military drills.

“This exercise has been planned for some time and is part of the air component of the Foal Eagle exercise,” spokesman George Little told reporters Monday.

Meanwhile, the North Korean leader gathered legislators Monday for an annual spring parliamentary session that followed a ruling party declaration that nuclear bomb building and a stronger economy were the nation’s top priorities.

The meeting of the Supreme People’s Assembly follows near-daily threats from Pyongyang, including vows of nuclear strikes on South Korea and the U.S.

North Korea said Saturday its armed forces, “will blow up U.S. bases for aggression in its mainland and in the Pacific operational theaters including Hawaii and Guam.”

Kim also threatened to shut down a border factory complex that is the last major symbol of inter-Korean cooperation.

The threats are seen as part of an effort to provoke the new government in Seoul to change its policies toward Pyongyang and to win diplomatic talks with Washington in order to gain more aid.

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

A senior U.S. official confirms to Fox News that the F-22 Raptors were deployed to Osan Air Base in South Korea from Japan on Sunday to support ongoing U.S.-South Korean military drills.

Meanwhile, North Korean leader Kim Jong Un gathered legislators Monday for an annual spring parliamentary session that followed a ruling party declaration that nuclear bomb building and a stronger economy were the nation’s top priorities.

The meeting of the Supreme People’s Assembly follows near-daily threats from Pyongyang, including vows of nuclear strikes on South Korea and the U.S. In a statement released Sunday, U.S. military in South Korea urged North Korea to restrain itself.

“(North Korea) will achieve nothing by threats or provocations, which will only further isolate North Korea and undermine international efforts to ensure peace and stability in Northeast Asia,” the statement said.

Meanwhile, North Korea said Saturday its armed forces, “will blow up U.S. bases for aggression in its mainland and in the Pacific operational theaters including Hawaii and Guam.”

Kim also threatened to shut down a border factory complex that is the last major symbol of inter-Korean cooperation, according to the Associated Press.

The threats are seen as part of an effort to provoke the new government in Seoul to change its policies toward Pyongyang and to win diplomatic talks with Washington in order to gain more aid.

The White House says the U.S. is taking North Korea’s threats seriously, but has also noted Pyongyang’s history of “bellicose rhetoric.”

On Thursday, U.S. military officials revealed that two B-2 stealth bombers dropped dummy munitions on an uninhabited South Korean island as part of annual defense drills that Pyongyang sees as rehearsals for invasion. Hours later, Kim ordered his generals to put rockets on standby and threatened to strike American targets if provoked.

Military analysts have said a full-scale conflict between North and South Korea is extremely unlikely, noting that the Korean Peninsula has remained in a technical state of war for 60 years. But the North’s continued threats toward South Korea and the United States have raised worries that a misjudgment between the sides could lead to a clash.

In addition to the military exercise, the U.S. will fortify its defenses against a potential North Korean missile attack by adding more than a dozen missile interceptors to the 26 already in place at Fort Greely, Alaska, Defense Secretary Chuck Hagel has also announced.

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

“From this time on, the North-South relations will be entering the state of war and all issues raised between the North and the South will be handled accordingly,” said a statement carried by the official North Korean news agency, according to a Reuters report.

The joint statement by the government, political parties and organizations said North Korea will deal with all matters involving South Korea according to “wartime regulations.” It also warned it will retaliate against any provocations by the United States and South Korea without “any prior notice.”

The divided Korean Peninsula is already in a technical state of war because the 1950-53 Korean War ended in a cease-fire, not a peace treaty. But Pyongyang said it was scrapping the war armistice earlier this month.

Reuters reported that North Korea’s statement said it would respond “without mercy” to any action by South Korea that harmed its sovereignty, indicating it was not about to mount a pre-emptive strike.

Analysts say a full-scale conflict is extremely unlikely and North Korea’s threats are instead aimed at drawing Washington into talks that could result in aid and boosting leader Kim Jong Un’s image at home. But the harsh rhetoric from North Korea and rising animosity from the rivals that have followed U.N. sanctions over Pyongyang’s Feb. 12 nuclear test have raised worries of a misjudgment leading to a clash.

South Korea’s Unification Ministry released a statement saying the latest threat wasn’t new and was just a follow-up to Kim’s earlier order to put troops on a high alert in response to annual U.S-South Korean military drills. Pyongyang sees those drills as rehearsals for an invasion; the allies call them routine and defensive.

In an indication North Korea is not immediately considering starting a war, officials in Seoul said South Korean workers continued Saturday to cross the border to their jobs at a joint factory park in North Korea that’s funded by South Koreans

On Friday, North Korean leader Kim Jong Un warned his forces were ready “to settle accounts with the U.S.” after two nuclear-capable U.S. B-2 bombers dropped dummy munitions on a South Korean island range as part of joint drills and returned to their base in Missouri.

North Korean state media later released a photo of Kim and his senior generals huddled in front of a map showing routes for envisioned strikes against cities on both American coasts. The map bore the title “U.S. Mainland Strike Plan.”

At the main square in Pyongyang, tens of thousands of North Koreans turned out for a 90-minute mass rally in support of Kim’s call to arms. Small North Korean warships, including patrol boats, conducted maritime drills off both coasts of North Korea near the border with South Korea earlier this week, South Korean Defense Ministry spokesman Kim Min-seok said in a briefing Friday. He didn’t provide details.

The spokesman said South Korea’s military was mindful of the possibility that North Korean drills could lead to an actual provocation. He said the South Korean and U.S. militaries are watching closely for any signs of missile launch preparations in North Korea. He didn’t elaborate.

Experts believe North Korea is years away from developing nuclear-tipped missiles that could strike the United States. Many say they’ve also seen no evidence that Pyongyang has long-range missiles that can hit the U.S. mainland.

Still, there are fears of a localized conflict, such as a naval skirmish in disputed Yellow Sea waters. Such naval clashes have happened three times since 1999. There’s also danger that such a clash could escalate. Seoul has vowed to hit back hard the next time it is attacked.

“The first strike of the revolutionary armed forces of the DPRK will blow up the U.S. bases for aggression in its mainland and in the Pacific operational theatres including Hawaii and Guam,” the North said Saturday in the statement carried by the official Korean Central News Agency. DPRK stands for the Democratic People’s Republic of Korea, the North’s official name.

Pyongyang uses the U.S. nuclear arsenal as a justification for its own push for nuclear weapons. It says that U.S. nuclear firepower is a threat to its existence.