Hagel's hopes of swift confirmation appear to rest with his one-time friend and colleague Senator John McCain, who sharply criticized Hagel at a confirmation hearing and has not yet made clear whether he would support a filibuster.

McCain's fellow Republican hawk Senator Lindsey Graham suggested that he would drop his delaying tactics only after the Senate returns from a weeklong recess in the week of Feb 25.

Both men on Thursday got a letter from the White House with new details of Obama's actions on the night of the attack by militants on the consulate in Benghazi, which killed four people, including US Ambassador Chris Stevens.

It confirmed that then-secretary of state Hillary Clinton had called Mohammed Megaryef, president of the Libyan national assembly, on the night of the Benghazi attack, but Obama had not.

Graham had argued that the extra weight of a demand by the US president, at a time when the consulate was under siege, might have mobilized Libyan forces more quickly and saved some American lives.

According to the letter from White House counsel Kathryn Ruemmler, Obama spoke to Megaryef on the night after the attack.

The letter prompted Graham to say he might drop resistance to a confirmation vote after the Senate break, a move which would clear the path for Hagel.

But he added a qualifier, saying "unless there's some bombshells, unless he (said) that the Israeli government is bloodsucking vampires or something like that, I got a feeling I'd be OK".

Hagel was picked to replace outgoing Pentagon chief Leon Panetta at a time of rising tension in Middle East hotspots, budget battles at home, and after this week's nuclear test by the Democratic People's Republic of Korea.

Panetta spent his last day at work on Thursday before returning to his home in California, but he will formally retain the responsibilities of defense secretary until his successor is confirmed.

Several Republicans have taken issue with Hagel's public stances in recent years on Iran, nuclear weapons, Israel and the US troop surge in Iraq.

Agence France-Presse