Sen. Lindsey Graham threatened Monday to hold up all nominations for federal government positions until survivors of last year’s deadly attack on the diplomatic post in Libya appear before Congress.

“Where are the #Benghazi survivors?” the South Carolina Republican said on his official Twitter account. “I’m going to block every appointment in the US Senate until they are made available to Congress.”

There have been a number of Capitol Hill hearings on the Sept. 11, 2012, attack in Benghazi, Libya, that killed Ambassador Chris Stevens and three other Americans. And there was a review chaired by former Ambassador Thomas Pickering and former Joint Chiefs Chairman Adm. Mike Mullen. But Graham is among lawmakers dissatisfied with information they’ve received so far and he has threatened previous nominations over the issue.

This time he’s calling for a special congressional committee to investigate.

“The State Department is blaming the CIA, the CIA is blaming the State Department. Where was the Department of Defense?” Graham said earlier Monday on the news show “Fox & Friends.” ”So I am calling for a joint select committee … where you get three or four committees together to look at this situation as one unit.”

Prominent nominations announced by President Barack Obama and awaiting Senate confirmation include Janet Yellen for chair of the Federal Reserve and Jeh Johnson for secretary of the Department of Homeland Security.

Under the U.S. Constitution, the president nominates — but the Senate must approve — a host of appointments including ambassadors, Supreme Court Justices, Cabinet members and military personnel being promoted to the rank of general officer. Graham is a longtime member of the Senate Armed Services Committee.

Graham complained on Fox that 14 months after the attack, people who survived it “have not been made available to the U.S. Congress for oversight purposes.”

The State Department rejects allegations that it has forbidden any of its employees from appearing before Congress.

It has noted that the Benghazi survivors have spoken to investigators and that those reports have been made available to lawmakers.

A 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, in which militants stormed the diplomatic post and set it on fire.

Benghazi stands as cause celebre for conservative Republicans who insist the administration was trying to mislead the American people during the heat of a presidential campaign, playing down a terrorist attack on Obama’s watch.

In February, Graham and Sen. John McCain, R-Ariz., led Republicans in blocking the Senate vote on Obama’s nomination of former Republican Sen. Chuck Hagel to serve as defense secretary, demanding information about the president’s actions in the aftermath of the deadly attack on the U.S. diplomatic mission in Benghazi.

The administration responded to the requests, and the Senate later confirmed Hagel.

Later that month, Republicans also threatened to hold up the nomination of CIA Director John Brennan, insisting on documents related to Benghazi. The administration provided emails and other documents to Congress.

Graham, who has drawn criticism in some Republican quarters for working with Democrats on other issues like immigration, has been highly critical of the administration on Benghazi. The two-term senator faces several Republican rivals in the GOP primary as he fights for re-election in South Carolina.

(AP)