WASHINGTON – A leading Republican senator said Sunday he would hold up Senate confirmation of President Obama’s nominees to head the Pentagon and the CIA until the White House provided more answers about the Sept. 11 attack against a U.S. installation in Benghazi, Libya.

The White House took aim at South Carolina Sen. Lindsey Graham, a persistent critic of Obama’s response to the terrorist assault, by urging quick approval of the president’s second-term national security team and scolding any lawmakers trying to “play politics” with critical nominations.

Graham accused the White House of “stonewalling” requests to release more information about the attack that killed four Americans, including the U.S. ambassador to Libya. “We’re going to get to the bottom of Benghazi,” he told CBS’ “Face the Nation.”

A Democratic colleague branded Graham’s threat to stall the nominations of former Sen. Chuck Hagel, R-Neb., to be defense secretary and John Brennan, Obama’s top counterterrorism adviser, to be CIA director as “unprecedented and unwarranted.” Senators should have the chance to vote on the fate of those nominees, said Sen. Jack Reed of Rhode Island.

The White House noted that Defense Secretary Leon Panetta and Army Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, testified Thursday before Congress about the chaotic day of the Sept. 11 attack.

In January, Graham had signaled he would delay Brennan’s pick and told Fox News he would “absolutely” block Hagel unless Panetta and Dempsey testified about the Benghazi attack. The senator said he was “happy as a clam” when he learned the hearing with Panetta and Dempsey had been scheduled.

Republicans have accused the Obama administration of an election-year cover-up of the attack and at the hearing, several suggested that the commander in chief was disengaged as Americans died.

“We know nothing about what the president did on the night of September 11th during a time of national crisis, and the American people need to know what their commander in chief did, if anything, during this eight-hour attack,” Graham said on CBS.

Graham contended that a six-person rescue team was delayed from leaving the Benghazi airport because of problems “with the militias releasing them and a lot of bureaucratic snafus,” and he said he wants to know whether Obama called any Libyan officials to expedite their mission.

Tommy Vietor, a spokesman for the White House’s National Security Council, said, “We believe the Senate should act swiftly to confirm John Brennan and Sen. Hagel. These are critical national security positions and individual members shouldn’t play politics with their nominations.”

Reed said that “to dwell on a tragic incident and use that to block people is not appropriate.”