Updated

Republican Sen. John McCain, a sharp critic of Chuck Hagel's nomination as defense secretary, said Monday he will not support a filibuster of President Barack Obama's pick, even though he declined to say whether he intends to vote for confirmation.

"I do not believe a filibuster is appropriate and I would oppose such a move," McCain told reporters Monday, two days after Senate Republican leader Mitch McConnell raised the possibility of forcing a showdown vote.

In the fiercest exchange of Hagel's confirmation hearing last week, McCain questioned the nominee about the Iraq war and whether he was right or wrong in opposing an additional 30,000 U.S. troops in 2007. The Arizona senator said he still has questions on the nomination and "was not happy with his (Hagel's) failure to answer a really simple question."

But McCain insisted he would not support use of the filibuster, a procedural tactic which can derail a confirmation vote and which can be stopped only by the votes of 60 of the 100 senators.

Several other Republican senators echoed McCain about a step that would be historic on a Cabinet choice. Nominees facing stiff opposition or serious ethical questions typically have withdrawn before any vote. The last nominee to be defeated was John Tower, President George H.W. Bush's choice for defense secretary who failed on a 53-47 vote in 1989 amid accusations of drinking and womanizing.

"It would be unprecedented for the Senate not to allow an up-or-down vote on a president's Cabinet nomination, but I haven't made any decision about a vote," said Sen. Lamar Alexander, R-Tenn.

Sen. Susan Collins, R-Maine, said she was "not inclined to support a filibuster regardless of my ultimate decision" on the nominee.

Republican Sen. Richard Burr of North Carolina, who opposes Hagel's nomination, said he would not support a filibuster.

Even Sen. Lindsey Graham, R-S.C., who suggested the administration re-evaluate its choice, said "filibustering is something I do very reluctantly."

In interview this past weekend, McConnell gave Hagel a poor grade for his testimony before the Senate Armed Services Committee and said opposition to the former Republican senator leading the Pentagon was growing.

"Whether that means he will end up having to achieve 60 votes or 51 is not clear yet," the Kentucky senator, who is seeking re-election, said Saturday at the opening of his campaign headquarters in Louisville.

Hagel seemed ill-prepared under withering cross-examination from committee Republicans in nearly eight hours of testimony last Thursday. He was repeatedly pressed about past statements and votes on Israel, Iran and nuclear weapons, with GOP lawmakers suggesting he wasn't sufficiently supportive of Israel or anti-Iran.

Senate Democrats, who hold the majority, continue to stand behind the nomination, and no Democrat has said he or she would vote against the president's pick for his second-term national security team. Hagel, 66, is a decorated Vietnam combat veteran who served two terms as Nebraska senator.

About a dozen Republican have said they will oppose their former colleague and several others have indicated they are likely to vote no.

Democrats hold a 55-45 advantage in the Senate and two Republicans have announced their support for Hagel -- Sens. Thad Cochran of Mississippi and Mike Johanns of Hagel's home state of Nebraska. Sen. Roy Blunt, R-Mo., a member of the leadership, said he would oppose Hagel, but would not back a filibuster.

McConnell's failure to rule out a filibuster marks the first time the leader has suggested it could be an option. In the past, when Republicans occupied the White House, GOP senators have argued strenuously that nominees should get an up-or-down Senate vote, especially Cabinet picks.

Last Friday, White House spokesman Jay Carney said the administration would be "stunned if, in the end, Republican senators chose to try to block the nomination of a decorated war veteran who was once among their colleagues in the Senate as a Republican."

The White House insisted on Monday that the president stands behind the nominee.

"The issue here is `how will an individual do the job,' and there's no question in the president's mind that Sen. Hagel will do the job well," Carney said aboard Air Force One.

The Senate Armed Services Committee could vote as early as Thursday on the nomination and refer it to the full Senate. Democrats hold a 14-12 edge on the panel.