WASHINGTON (AP) — A leading Republican senator said Sunday he would hold up Senate confirmation of President Barack Obama's nominees to head the Defense Department and the CIA until the White House provided more answers about the deadly Sept. 11 attack against a U.S. installation in Benghazi, Libya.

The White House took aim at 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.

A Democratic colleague branded Graham's threat to stall the nominations of former Sen. Chuck Hagel 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.

The White House did not address Graham's demand for more information, but did note that Defense Secretary Leon Panetta and Army Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, testified Thursday before Congress about the chaotic day of the Sept. 11 attack.

Republicans have accused the Obama administration of an election-year cover-up of the attack, and at the hearing several suggested 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.

"I don't think we should allow Brennan to go forward for the CIA directorship, Hagel to be confirmed to secretary of defense until the White House gives us an accounting," Graham said, adding, "What did he do that night? That's not unfair. The families need to know, the American people need to know."

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. To try to find information, to ask legitimate questions, as Senator Graham is doing is completely appropriate. But then to turn around and say, 'I'm going to disrupt, essentially, the nomination of two key members of the President's Cabinet,' I don't think that's appropriate, I don't think it's warranted, I think it is an overreaction that is not going to serve the best interest going forward of the national security of the United States."

Graham would have none of it.

"In a constitutional democracy, we need to know what our commander in chief was doing at a time of great crisis, and this White House has been stonewalling the Congress, and I'm going to do everything I can to get to the bottom of this so we'll learn from our mistakes and hold this president accountable for what I think is tremendous disengagement at a time of national security crisis," he said.

At the Senate hearing, Panetta testified that he and Dempsey were meeting with Obama when they first learned of the Libya assault. He said the president told them to deploy forces as quickly as possible. Graham asked whether Panetta spoke again to Obama after that first meeting. Panetta said no, but that the White House was in touch with military officials and aware of what was happening. At one point, Graham asked Panetta if he knew what time Obama went to sleep that night. The Pentagon chief said he did not.