The leaders of the panel that independently reviewed last year’s deadly attack on the U.S. diplomatic mission in Benghazi, Libya, said Tuesday they were prepared to testify publicly before Congress to counter what they consider unfounded criticism of their work.

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.

The announcement came on the same day that the Senate Foreign Relations Committee approved President Barack Obama’s nominee for U.S. ambassador to Libya, a post that has been vacant since the insurgent attack Sept. 11, 2012, that killed Ambassador Chris Stevens and three other Americans.

With little discussion, the panel on a voice vote approved Deborah Kay Jones, a career diplomat who has served in Kuwait, Argentina, Syria, Iraq and Turkey.

At her confirmation hearing earlier this month, Jones promised to work to ensure sufficient security at U.S. facilities, saying the ambassador was the principle security officer and vowing to simply pick up the phone and call Washington if she felt security was lax.

Meanwhile, 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 Benghazi attack.

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.

Earlier this week, Rep. Darrell Issa, R-Calif., chairman of the House Oversight and Government Reform Committee, asked Pickering and Mullen to meet privately with committee staff 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.

On Monday, Sen. Bob Menendez, D-N.J., chairman of the committee, praised the nominee and spoke of the imperative of filling the job amid increasing lawlessness in Libya.

“There is simply no substitute for having a confirmed U.S. ambassador on the ground, reaching outside the wire to the Libyan people as they shape a safer, more productive and inclusive future,” Menendez said.

If confirmed by the full Senate, Jones would take over an ambassadorship that has been vacant for nearly eight months.