WASHINGTON – A moderate Republican senator once thought to be a possible backer of Chuck Hagel’s nomination to be secretary of defense said she’ll oppose his confirmation, while other Republican senators signaled they may delay a floor vote on the nomination unless the White House provides more information about the deadly attack on the U.S. diplomatic mission in Benghazi, Libya.

Sen. Susan Collins, R-Maine, said Wednesday that Hagel’s views on the most critical threats facing the United States are “unsettling.” In a four-page statement, Collins said Hagel was unwilling to ask the European Union to designate Hezbollah a terrorist organization in 2006, and he has been hesitant to back the use of all non-military options, such as unilateral sanctions, to pressure Iran into ceasing its nuclear program.

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Sen. Susan Collins, R-Maine, a moderate who was once thought to be a backer of Chuck Hagel’s nomination for defense secretary, now says she’ll oppose his confirmation. The Associated Press

Former Republican Sen. Chuck Hagel, President Obama's nominee for Secretary of Defense The Associated Press

Senate Majority Leader Harry Reid, D-Nev., set the stage for a full Senate vote on Hagel, President Obama’s choice to succeed Defense Secretary Leon Panetta. Reid filed a motion to limit debate and force a vote, which is expected to be held Friday. Democrats hold a 55-45 edge in the Senate and have the numbers to confirm Hagel on a majority vote, but would need the support of five Republicans to clear the way for an up-or-down vote on Hagel.

A president’s pick for a Cabinet post usually requires only a majority vote, leading Reid to accuse Senate Republicans of orchestrating a filibuster against a nominee for secretary of defense for the first time in the country’s history.

But the top Republican on the Senate Armed Services Committee said it’s not unusual to hold a Cabinet nominee to a 60-vote threshold. “It’s not a filibuster,” said Sen. James Inhofe, R-Okla. “This has happened, and it’s happening again right now.”

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 their opposition to their onetime colleague, a former two-term Republican senator from Nebraska and twice-wounded Vietnam combat veteran.

Sen. Lindsey Graham, R-S.C., said Wednesday that he would vote against ending debate on Hagel’s nomination to be defense secretary because he wants more information on Obama’s actions on the night of the Sept. 11 raid on the mission in Benghazi. Ambassador Chris Stevens and three other Americans died.

Graham, Sen. John McCain, R-Ariz., and Sen. Kelly Ayotte, R-N.H., wrote to Obama on Tuesday and asked whether he spoke to any Libyan government official during the assault.

Sen. Carl Levin, D-Mich., the chairman of the Armed Services Committee, said he’s confident the White House will supply the information and that Hagel will be confirmed.

Collins, who serves on the Senate Intelligence Committee, said she would not join in a filibuster to block a final vote.

In her statement, Collins said Hagel’s “courageous military service deserves our praise and gratitude” and that he cares deeply about the welfare of the troops. But she could not get past what she described as Hagel’s troubling record on key national security issues. Confirming him would send the wrong message to the country’s allies and adversaries about the resolve of the U.S., Collins said.

“I am unable to support Senator Hagel to be the next secretary of defense because I do not believe his past positions, votes, and statements match the challenges of our time, and his presentations at his (confirmation) hearing did nothing to ease my doubts,” Collins said.

Republican Sens. Thad Cochran of Mississippi and Mike Johanns of Nebraska have voiced their support for Hagel.