Sen. Lindsey Graham, R-S.C., called on Congress to set up a special committee to investigate the Obama administration's response to the Sept. 11, 2012, attack on a U.S. diplomatic post in Benghazi, Libya.

Several congressional panels have held Benghazi-related hearings since 2012. But Graham said that because of the case's complexities and the Obama administration's reluctance to cooperate with Congress, a new, bipartisan joint House-Senate "select committee" is needed to coordinate what has been a mostly Republican investigation.

“For too long we have had various House and Senate committees, along with the State Department's Accountability Review Board investigating the small pieces of Benghazi within their jurisdictions," Graham said Friday. "These are sometimes disjointed and do not always allow for a full and thorough investigation."

The senator said a joint select committee is the "best means to ensure Benghazi is fully investigated and all questions are answered once and for all."

The administration originally said the assault — which killed U.S. Ambassador Christopher Stevens and three other Americans — was spontaneous and linked to protests earlier that day in Cairo against an American-made video denigrating Islam's prophet Muhammad. But Republicans have said the evidence shows that the administration knew it was a planned attack by an organized anti-American terrorist group.

The last special joint committee convened on Capitol Hill was 2011's so-called supercommittee, which was set up to find ways to reduce the federal government's ballooning deficit. Its failure trigged the automatic "sequester" spending cuts that began in early 2013.

Graham's comments come a day after House Intelligence Committee Chairman Mike Rogers said he likely will recall former CIA Acting Director Mike Morell to testify before his panel. Some Republicans have accused Morell of misleading Congress over the White House's role in crafting the Benghazi talking points.

Graham also wants National Security Adviser Susan Rice, who has briefed Congress several times regarding the Benghazi attack, to testify again on Capitol Hill. Republicans have accused her of giving misleading statements in the days immediately following the attack.

The Republican senator added he wants the administration to declassify all communications regarding the attack.

"The president has said on numerous occasions that as more information is made available [on Benghazi] he would share it with the public. This statement has not borne fruit," Graham said.

"It’s past time we clear the air on Benghazi by declassifying all relevant information and having all witnesses testify."