In a letter to the House Oversight and Government Reform Committee, veteran diplomat Thomas Pickering said he and former Joint Chiefs Chairman Adm. Mike Mullen would answer any questions lawmakers have. Rep. Darrell Issa, R-Calif., chairman of the panel, is pressing for the two men to agree to an interview with staff investigators prior to a public hearing.

The work of the Accountability Review Board is the latest focus of a broader Republican inquest into their claims that the Obama administration misled Congress and the American people after the Sept. 11, 2012, attack that killed Ambassador Chris Stevens and three other Americans.

The blistering report released in December by Pickering, Mullen and three other reviewers found that “systematic failures and leadership and management deficiencies at senior levels” of the State Department meant security was “inadequate for Benghazi and grossly inadequate to deal with the attack that took place.”

Pickering, however, noted how recently “some have called into question the integrity of the board and its work.”

“We believe that such criticisms are unfounded and, if left unaddressed, undermine the essential work that the board has done,” he wrote. “It is therefore important that we be afforded the opportunity to appear at a public hearing before the committee and answer directly questions regarding the board’s procedures, findings and recommendations.”

Republicans believe the report was flawed, and they want to know why top officials like Secretary of State Hillary Rodham Clinton weren’t interviewed. The panel absolved Clinton of any wrongdoing, faulting lower level State Department officials. Four were given paid suspensions.

On Monday, Issa asked Pickering and Mullen to meet privately with committee staff investigators to answer questions about their review. Democrats countered that if lawmakers wanted to talk to them, Issa should hold a full open hearing.

Pickering said the board “conducted a thorough review and produced a report that included detailed findings and frank and often highly critical assessments.” It issued 29 recommendations for improving security at diplomatic facilities worldwide, and Pickering insisted that the board “fulfilled its role in identifying the lessons that must be learned and acted upon from Benghazi.”

“We stand behind the board’s report and look forward to discussing it in a public hearing,” he wrote.

Frederick Hill, a spokesman for the committee, said late Tuesday that the panel was following up with Pickering and the State Department to determine whether he would appear voluntarily for an interview with committee staff investigators. Hill noted that Issa and Pickering appeared on a Sunday talk show together two days ago, and said the former diplomat had told the committee chairman that he would voluntarily submit to an interview.

“The committee is giving him a full opportunity to voluntarily follow through on his commitment,” Hill said.

Issa, in his letter on Monday to Pickering and Mullen, had said that following the private interview, the committee would work with the report’s authors on a date for a public hearing.

Initial versions, as has been previously reported, contained references to Al Qaeda that were later deleted. But the latest excerpts show how State Department spokesman Victoria Nuland pressed the CIA to scrub references to the agency’s prior security warnings.

According to ABC News, the original paragraph read:

“The Agency has produced numerous pieces on the threat of extremists linked to al-Qa’ida in Benghazi and eastern Libya. These noted that, since April, there have been at least five other attacks against foreign interests in Benghazi by unidentified assailants, including the June attack against the British Ambassador’s convoy. We cannot rule out the individuals has previously surveilled the U.S. facilities, also contributing to the efficacy of the attacks.”

But Nuland wrote that the lines  “could be abused by members [of Congress] to beat up the State Department for not paying attention to warnings, so why would we want to feed that either? Concerned …”

The paragraph in question was then reportedly deleted.

The Weekly Standard, which referenced that exchange briefly in a prior account, also reported new details Friday, describing how then-CIA Director David Petraeus voiced surprise when he learned the Saturday after the attack that officials had deleted all prior references to Al Qaeda and jihadists, leaving only the word “extremists.”

U.S. Ambassador to the U.N. Susan Rice would use the final version of the talking points to say on several Sunday shows that the attack was triggered by protests over an anti-Islam film.

While administration officials and congressional Democrats have described the protracted debate over the talking points as politically motivated and inconsequential, the testimony this week drew new attention to it.

Greg Hicks, former deputy chief of mission in Libya, said Rice’s comments actually hurt the FBI investigation by insulting the Libyan president — who gave a conflicting account at the time by saying the attack was premeditated.

Hicks said the anti-Islam film was actually a “nonevent” in Libya, and his “jaw dropped” when he heard Rice’s comments.

ABC News reported that the CIA’s first drafts did say the attack appeared to be “spontaneously inspired” by the protests at the embassy in Cairo. However, the early versions also said “we do know that Islamic extremists with ties to al-Qa’ida participated in the attack.”

The State Department and White House have continued to defend their actions and intervention in light of the new details.

After it was first revealed that references to security concerns — in addition to references to Al Qaeda — were removed, White House Press Secretary Jay Carney said: “What we said and what remains true to this day is that the intelligence community drafted and redrafted these points.”

He defended administration claims that the faulty statements were merely the product of incomplete intelligence in a rapidly changing environment. Despite the excerpts, he stood by claims that White House involvement was minimal.

“The fact that there are inputs is always the case in a process like this. But the only edits made by anyone here at the White House were stylistic and non-substantive. They corrected the description of the building or the facility in Benghazi from ‘consulate’ to ‘diplomatic facility’ and the like,” he said.

State Department spokesman Patrick Ventrell also said Rice’s comments were based on the intelligence community’s “best assessment that there was not any evidence of months-long pre-planning or pre-meditation, which remains their assessment.”

On the heels of a dramatic hearing where three whistle-blowers testified, Fox News has learned that former Vice President Dick Cheney on Thursday, on the Hill for a meeting with House Republicans, also told lawmakers: “I think Hillary (Clinton) should be subpoenaed if necessary.”

The comments and developments signal that Republicans will continue to press for answers on the deadly Sept. 11 attack. Despite arguments from Democrats that the hearing was not nearly as shocking as Republicans made it out to be, GOP lawmakers said it raised troubling questions that need to be investigated.

“The truth shouldn’t be hidden from the American people behind a White House firewall,” Boehner said Thursday. “Four Americans lost their lives in this terrorist attack. Congress will continue to investigate this issue, using all of the resources at our disposal.”

Boehner specifically urged the Obama administration to make public a set of internal emails that some lawmakers had been able to review but not keep.

One of the emails apparently showed a top State Department official saying a group affiliated with Islamic terrorists was responsible for the strike. Separate emails, though, allegedly depict the White House and State Department pressing lower-level officials to remove references to terrorism in talking points about the attacks.

Based on those talking points, U.N. Ambassador Susan Rice would go on five Sunday talk shows shortly after the attacks to claim they were triggered by protests over an anti-Islam film. Top officials would later claim the flawed assessment was based on the best intelligence at the time, but the testimony from whistle-blowers Wednesday indicated that those on the ground knew the attack was terrorism.

“The YouTube video was a non-event in Libya,” Greg Hicks, deputy chief of mission in Libya, testified Wednesday.

After the hearing, Republican Rep. Darrell Issa said he will continue to seek whistle-blowers to “come forward.”

“Candidly, as quickly as possible, we simply want to have the whistleblowers that are still out there, in fact witnesses that are still out there to come forward, tell us their story. We will get it out and we will close up this investigation,” he told Fox News.

Issa, R-Calif., is chairman of the House Oversight and Government Reform Committee, which held the hearing.

The wide-ranging and dramatic testimony Wednesday raised several fresh questions about the attack. Witnesses questioned why security had not been tightened in Benghazi in the months leading up to the assault and why U.S. military assets did not respond sooner that night, with one alleging a military team was not given permission to fly from Tripoli to Benghazi the next morning.

Further, they raised serious concerns about the administration’s initial decision to describe the attack as a protest gone awry despite evidence on the ground to the contrary.

In startling testimony, Hicks also claimed the State Department retaliated against him after he raised questions about that decision. He claimed that Assistant Secretary of State for Near Eastern Affairs Elizabeth Jones delivered a “blistering critique” of his management style after he criticized Rice’s initial claim that the attack was tied to anger over an anti-Islam film. He also claimed that he was counseled to avoid personally discussing the attack with Republican Rep. Jason Chaffetz and was “effectively demoted” to a desk officer in the end.

Issa, in a written statement after Wednesday’s hearing, called the alleged retaliation and intimidation “perhaps most troubling.”

Rep. Elijah Cummings, D-Md., top Democrat on the committee, vowed to protect the whistle-blowers while criticizing his Republican colleagues for allegedly trying to politicize the tragedy. He claimed afterward that the testimony only served to undercut Republican allegations.

“What should have been a bipartisan investigation involving our national security was another sorry example of Republicans promising explosive new facts but delivering only a press spectacle,” he said in a statement.

The committee may move to hear testimony next from at least one leader of the State Department’s internal review of the Benghazi attack. Though the leaders, former Joints Chiefs of Staff Adm. Mike Mullen and former Ambassador Thomas Pickering, apparently declined to testify, Pickering told MSNBC on Wednesday that he is willing to speak.

Issa spokesman Frederick Hill on Thursday noted the “change of heart” — but also said neither Pickering nor the administration has contacted the committee about possible testimony.

Several claims from Wednesday’s hearing could open up new lines of inquiry on the attack and its aftermath. Among them, Hicks claimed that Rice’s faulty claims about the nature of the attack hurt the FBI investigation.

Hicks argued that Rice’s comments so insulted the Libyan president — since they contradicted his Sept. 16 claims that the attack was premeditated — that it slowed the FBI’s investigation.

“President Magariaf was insulted in front of his own people, in front of the world. His credibility was reduced,” Hicks said, adding that the president was apparently “still steamed” two weeks later.

This bad blood, he claimed, contributed to the FBI team being stuck in Tripoli for about 17-18 days.

“I definitely believe that it negatively affected our ability to get the FBI team quickly to Benghazi,” he said, adding that the U.S. could not even get the Libyans to secure the crime scene during that time.

The claim was one of several new accounts given at Wednesday’s high-profile hearing where three whistle-blowers testified.

Democrats, while giving deference to the officials and their version of events, used the hearing to try and deflect criticism away from the administration. In particular, they rejected the notion that early talking points on the attack were deliberately changed, to downplay terrorism, for political reasons.

“People who have actually seen the documents, who have actually conducted a real investigation completely reject the allegation that they were made for political purposes,” Rep. John Tierney, D-Mass., said.

But the substance of the claims Wednesday could serve to re-open questions about that deadly night — and specifically about the initial claim by U.N. Ambassador Susan Rice that the attack was triggered by a protest over an anti-Islam film.

Greg Hicks, the deputy chief of mission in Libya who became the top U.S. diplomat in the country after Ambassador Chris Stevens was killed, was asked to respond to former Secretary of State Hillary Clinton’s statement at a prior hearing asking “what difference” do the questions over the talking points make.

Hicks argued that Rice’s comments so insulted the Libyan president — since they contradicted his Sept. 16 claims that the attack was premeditated — that it slowed the FBI’s investigation.

“President Magariaf was insulted in front of his own people, in front of the world. His credibility was reduced,” Hicks said, adding that the president was apparently “still steamed” two weeks later.

This bad blood, he claimed, contributed to the FBI team being stuck in Tripoli for about 17 days.

“I definitely believe that it negatively affected our ability to get the FBI team quickly to Benghazi,” he said, adding that the U.S. could not even get the Libyans to secure the crime scene during that time.

As for Rice’s comments that Sunday, when she repeatedly cited the video as the trigger for the attack, Hicks said his “jaw dropped” when he heard that.

“I was stunned,” Hicks said. “My jaw dropped, and I was embarrassed.”

He said Rice never talked to him before those appearances.

Hicks said the only information coming out of his team was that there was an “attack” on the consulate. “The YouTube video was a non-event in Libya,” he said.

He also claimed that, when he asked a superior about the interviews, he was told “he should not proceed” with his questions. He was later given a “blistering critique” of his management style and effectively demoted to “desk officer,” he claimed.

Hicks’ testimony marked some of the most detailed of any delivered Wednesday. He and others also suggested the State Department’s internal review into the attack was lacking. Hicks said when he was interviewed by the group, a stenographer was not present.

In hours of testimony, the witnesses recounted in great detail what happened in eastern Libya on Sept. 11 and how U.S. personnel came under a series of attacks that left four Americans dead. Though Democratic officials have argued the attack has been thoroughly investigated and that the hearing Wednesday was political in nature, the claims challenged several long-standing assertions by the Obama administration.

The witnesses criticized the lax security at the Benghazi site in the run-up to the attack, and suggested the military did not do all it good to respond to the scene that night despite claims to the contrary.

Hicks also revealed that it appeared some were trying to lure even more U.S. personnel into a separate “ambush” while the attack was still being carried out. He described how, as diplomatic officials were trying to find out what happened to Stevens, they were receiving phone calls from supposed tipsters saying they knew where the ambassador was and urging Americans to come get him.

“We suspected that we were being baited into a trap,” Hicks said, adding that he did not want to send anybody into what he suspected was an “ambush.”

Getting choked up, Hicks described how the Libyan prime minister later called him to tell him Stevens was in fact dead. “I think it’s the saddest phone call I’ve ever had in my life,” he said.

At the very beginning of the attack, before Stevens went missing and was later found dead, Hicks said his team believed it was terrorism. He said a regional security officer rushed into his villa yelling, “Greg, Greg, the consulate’s under attack.”

He then spoke by phone with Stevens who told him the same: “Greg, we’re under attack.”

After enduring a night of attacks on the U.S. consulate, Hicks said the team departed at dawn for the nearby annex — shortly after they arrived, “the mortars came.”

Another whistle-blower questioned Wednesday why more military assets were not deployed sooner during the Benghazi terror attack. Mark Thompson, a former Marine and official with the State Department’s Counterterrorism Bureau, said he was rebuffed by the White House when he asked for a specialized team — known as a FEST team — to be deployed. This is a unit made of special operations personnel, diplomatic security, intelligence and other officers.

Suggesting that some were hesitant to deploy because they were unsure what was happening, “One definition of a crisis is you do not know what’s going to happen in two hours,” he said.

Further, Hicks explained how a separate team of special forces personnel were not given the authorization to fly from Tripoli to Benghazi. “They were furious,” he said.

Rep. Darrell Issa, chairman of the oversight committee holding the hearing, defended the witnesses, calling them “actual experts on what really happened before, during and after the Benghazi attacks,” who “deserve to be heard.”

The three witnesses were Hicks, Thompson and Eric Nordstrom, a diplomatic security officer who was formerly the regional security officer in Libya; and Thompson.

“I am a career public servant,” Hicks said. “Until the aftermath of Benghazi, I loved every day of my job.”

Nordstrom choked up as he began to testify Wednesday.

Rep. Elijah Cummings, D-Md., top Democrat on the oversight committee, said Wednesday that Republicans are using the witnesses’ statements for “political purposes.” He said he’s glad the whistle-blowers are testifying and would ensure they are protected, but pre-emptively challenged some of their claims — including the claim that U.S. military could have responded sooner to the site of the attack.

The Obama administration has adamantly denied several of the latest charges, including a claim that then-Secretary of State Hillary Clinton and a key aide tried to cut the department’s own counterterrorism bureau out of the chain of reporting and decision-making on Sept. 11. The administration also denied that the whistle-blowers in question were intimidated — while behind the scenes questioning the credibility of the witnesses.

A “fact sheet” released by the department ahead of the hearing reiterated its denials. The statement said the department has “demonstrated an unprecedented degree of cooperation with the Congress” on Libya, and rejected claims that the military was in a position to help that night but was told to stand down. Citing its internal review, the statement noted the review “found no evidence of any undue delays in decision making or denial of support from Washington or from the military combatant commanders.”

The other statement, by Mark Thompson of the State Department Counterterrorism Bureau, is mostly biographical. Testimony also is due Wednesday from Eric Nordstrom, a diplomatic security officer who was formerly the regional security officer in Libya.

The administration has parried Republican allegations lately by arguing that the attack is old news, that the State Department already has investigated it and that Republicans are engaged in a political witch hunt.

But a series of carefully timed leaks on the whistle-blowers’ testimony indicates House Republicans could have the goods to at least merit a second look at the administration narrative.

“The question is, where’s the accountability for lying to the American people?” Rep. Darrell Issa, R-Calif., chairman of the House Oversight and Government Reform Committee, told Fox News. “The American people were lied to.”

Issa claimed one “cover-up” is “undeniable” — that the State Department botched security in Benghazi in the run-up to the attack. But, he said, “it still doesn’t explain the president misleading the American people over a period of weeks.”

Three whistle-blowers are set to testify shortly before noon to the oversight committee Issa chairs.

Issa’s Democratic counterpart on the committee, Maryland Rep. Elijah Cummings, voiced skepticism about the leaks of the witnesses’ claims in advance of the hearing.

“If there was any matter that cries out for bipartisanship, it’s this,” he told Fox News, while raising criticisms that information about some witnesses wasn’t available in advance to Democrats. “This is about making sure that our diplomatic core are safe. … I want to go wherever the evidence leads, but I want all the evidence.”

Rep. Jason Chaffetz, R-Utah, a member of that committee, said if it weren’t for lawmakers’ persistence, “we would be left with a whole host of lies coming out of this administration, because they were not truthful about this.”

The “truth” surrounding the Benghazi attack has been elusive. The Obama administration has adamantly denied several of the latest charges, including a claim that then-Secretary of State Hillary Clinton and a key aide tried to cut the department’s own counterterrorism bureau out of the chain of reporting and decision-making on Sept. 11. The administration also denied that the whistle-blowers in question were intimidated — while behind the scenes questioning the credibility of the witnesses.

The witnesses are expected to cover a breadth of material in their testimony Wednesday. Lawmakers have questioned to what extent security requests were ignored before the attack, whether the military could have done more to respond the night of the attack and whether talking points were intentionally changed for political reasons after the attack to downplay terrorism. The witnesses could address all three areas on Wednesday.

A key area of interest is how the attack was described in the immediate aftermath.

The Weekly Standard reported last week that the initial CIA talking points on the attack said “Islamic extremists with ties to al Qaeda participated in the attack.” The reference to Al Qaeda was later taken out, and the initial reference to “attacks” was reportedly changed to “demonstrations.”

According to The Weekly Standard, State Department spokeswoman Victoria Nuland raised “serious concerns” at the time about the draft, concerned it could fuel criticism of the department.

The language continued to be watered down.

Issa told Fox News, in reference to the revisions, that “it’s very clear … that this was a political change.”

State Department officials released a statement Tuesday night labeled “Benghazi Attack Fack Check” to defend its security efforts.

“No one is more determined than the State Department family to bring those who perpetrated this attack to justice and do everything we need to do to keep our people safe,” the statement reads. “That’s where our attention is, and we hope Congress and the media, too, can keep the focus.”

Hicks, according to a transcript, also told congressional investigators that he thought it “was a terrorist attack from the get go.”

The whistle-blowers will be able to provide a new perspective on what was happening on the ground that night.

Hicks, according to transcripts, told investigators that the U.S. military could have prevented one wave of the deadly attack on American personnel in Benghazi if fighter jets had been promptly deployed. Further, he claimed that a second rescue team that was supposed to go from Tripoli to Benghazi early the next morning was told not to go.

He said Special Forces personnel were planning to board a C-130 flight at around 6 a.m. local time on Sept. 12 but got a phone call when they were on their way to the flight telling them “you can’t go now, you don’t have authority to go now. And so they missed the flight.”

He added: “They were told not to board the flight, so they missed it,” apparently because they did not have the “right authority.”

Thompson has also claimed that Clinton and a key aide effectively tried to cut the department’s own counterterrorism bureau out of the loop that night.

White House Press Secretary Jay Carney denied the claim on Monday.

Daniel Benjamin, who ran the department’s Counterterrorism Bureau at the time, also put out a statement Monday morning strongly denying the charges.

“I ran the bureau then, and I can say now with certainty, as the former Coordinator for Counterterrorism, that this charge is simply untrue,” he said. “Though I was out of the country on official travel at the time of the attack, I was in frequent contact with the Department. At no time did I feel that the Bureau was in any way being left out of deliberations that it should have been part of.”