WASHINGTON -- Republican senators blocked former Sen. Chuck Hagel's nomination to be President Barack Obama's next secretary of defence at least temporarily Thursday, as they demand more information on last year's attack on the U.S. diplomatic mission in Benghazi, Libya.

The Senate came up two votes short of the 60 needed to move Hagel's nomination forward as lawmakers prepare to leave town for a week's break. Democrats hold a 55-45 edge in the Senate, which must confirm cabinet secretaries and other high-profile appointees.

Rejections are extremely rare. Senate Majority Leader Harry Reid said such a move was unprecedented.

Hagel, a former Republican senator and twice-wounded Vietnam combat veteran, has already faced sharp questioning from his former colleagues over his past statements and votes on Israel, Iran, Iraq and nuclear weapons.

Senate Republicans also want more information about what Obama was doing on the night of the deadly attack on the U.S. diplomatic mission in Benghazi, Libya, in September. The attack killed the U.S. ambassador.

The White House responded on Wednesday to the Republicans' request for information about Benghazi, Reid said. "But now Republicans say this is not enough," Reid said. "This is no way to operate."

Reid filed a motion Wednesday to limit debate and force a full Senate vote.

The White House on Thursday said Obama did not speak to any Libyan government officials until the night after the attack. White House counsel Kathryn Ruemmler sent a letter Thursday to three Republican senators saying former Secretary of State Hillary Clinton called Libyan President Mohamed Magariaf on Obama's behalf on Sept. 11 to co-ordinate additional support to protect Americans in Libya.

Ruemmler said Obama spoke to Magariaf on the evening of Sept. 12.

A White House official said there was no new information in Ruemmler's letter. The fact of Clinton's call to Magariaf has previously been public. If there were a need to push the Libyans to do something, Obama would have called, but the Libyans were trying to do the right thing and were being as helpful as possible, the official said.

The official, discussing internal communications only on the condition of anonymity, said that it wasn't clear that an earlier call from Obama to the Libyans would have been helpful in the deadly, fast-moving assault.

A bitterly divided Armed Services Committee on Tuesday voted to approve Hagel by a 14-11 vote, with all the panel's Democrats backing him. The committee's Republicans were unified in opposition to their onetime colleague, who will succeed Defence Secretary Leon Panetta if he's confirmed.

Panetta on Thursday said the struggle over Hagel is getting on his nerves. "The second-best Valentine's Day present would be to allow Sylvia and I to get the hell out of town," he quipped at a Pentagon award ceremony for former Secretary of State Hillary Rodham Clinton.

While Democrats hold a 55-45 edge in the Senate and have the numbers to confirm Hagel on a majority vote, they need the support of five Republicans to clear the way for an up-or-down vote on him.

Sen. Lindsey Graham, a Republican, said he'll vote against ending debate on Hagel's nomination, and Sen. John McCain, another Republican who most sharply questioned Hagel during his Senate hearing, may join him.

They want to know whether Obama spoke to any Libyan government official during the assault and requested assistance for the American personnel at the mission. U.S. Ambassador Chris Stevens and three other Americans died in the raid at the compound in Benghazi.

The nomination of John Brennan as CIA director is also being delayed; the Senate Intelligence Committee is pushing off a vote amid demands that the White House turn over more details about drone strikes against terror suspects and about the Benghazi attacks. Intelligence Committee Chairwoman Dianne Feinstein, a Democrat, said a vote likely will be postponed till late February.

A president's pick for a Cabinet post usually requires only a majority vote -- not a supermajority of 60 votes -- leading Reid to accuse Senate Republicans of blocking a nominee for defence secretary for the first time in the country's history.

But the top Republican on the Senate Armed Services Committee challenged Reid's claim, saying it's not unusual to hold a Cabinet nominee to a 60-vote threshold. "This has happened (before), and it's happening again right now," said Sen. James Inhofe.

Sen. Carl Levin, the Democrat and chairman of the Armed Services Committee, said he's confident that the White House will supply the information Graham and McCain want and that Hagel will be confirmed.