The White House said Monday a top Republican was harming national security by delaying confirmation of new Pentagon and CIA chiefs in a row over the US consulate attack in Benghazi.

Republican Senator Lindsey Graham warned Sunday he would block Chuck Hagel's Senate confirmation as defense secretary and John Brennan's as CIA director, unless the White House offered more information on the September 11 assault.

Spokesman Jay Carney, however, said the White House had answered all questions about the militant strike, which killed four Americans, and accused critics of shifting goalposts after repeated testimony by officials about the incident.

"What is unfortunate here is the continuing attempt to politicize an issue... through nominees that themselves had nothing to do with Benghazi, and to do so in a way that only does harm to our national security interests," he said.

Senate Armed Services Committee chairman Senator Carl Levin said he would schedule a delayed vote to move Hagel's nomination to the full Senate on Tuesday.

The vote was put off last week, as Republicans assailed Hagel over his views on Iran, Israel and his stance on the war in Iraq.

Republicans on the committee had also demanded more details from Hagel on paid speeches he made between leaving the Senate in 2009 and his nomination to run the Pentagon during Obama's second term.

Graham has threatened to block Hagel until the White House was forthcoming about President Barack Obama's actions in response to the attack.

Under parliamentary rules, a single senator can prevent nominations from coming to a full Senate vote.

Carney argued that with more than 60,000 US troops still in Afghanistan, and other key international issues needing attention, it was detrimental to US national security for Obama's two nominees to be blocked.

"Senator Hagel, Mr Brennan, they need to be confirmed. They're highly qualified candidates for their posts. And we call on the Senate to act quickly to do just that," he said.

Graham warned on CBS television's "Face the Nation" that there would be "no confirmation without information" saying that president was "disengaged" on September 11 during the attack.

He demanded to know whether Obama had picked up the telephone to talk to Libyan leaders on that night and claimed that if he had, two of the four Americans killed that night could still be alive.

"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."

One of Graham's frequent Republican allies, Senator John McCain, said that though he was disappointed in Hagel's performance at a contentious confirmation hearing, the ex-senator had provided sufficient detail on his personal finances to the committee.

"I will not participate in any walkout of tomorrow's committee vote -- an action that would be disrespectful to Chairman Levin and at odds with the best traditions of the Senate Armed Services Committee," he said.