WASHINGTON — Senate Republicans on Thursday blocked the nomination of former GOP senator Chuck Hagel as the nation’s next defense secretary over unrelated questions about President Barack Obama’s actions in the aftermath of the deadly raid on the U.S. diplomatic mission in Libya.  Obama accused Republicans of playing politics with national security during wartime, and Democrats vowed to revive the nomination after Congress’ weeklong break.

By 58-40, with one abstention, the Senate fell short of the 60-vote threshold required to advance Hagel’s nomination to a final, up-or-down vote on his confirmation. Four Republicans voted with Democrats to end the debate and proceed to a final vote: Sens. Thad Cochran of Mississippi, Lisa Murkowski of Alaska, Susan Collins of Maine and Mike Johanns of Nebraska.

Obama reacted immediately, hammering Republicans for an unprecedented filibuster of a nominee for defense secretary and insisting that Hagel — a former two-term Republican senator from Nebraska and twice-wounded Vietnam combat veteran — will eventually win confirmation. He would succeed Defense Secretary Leon Panetta, who is stepping down after four years as CIA director and Pentagon chief.

“It’s just unfortunate that this kind of politics intrudes at a time when I’m still presiding over a war in Afghanistan and I need a secretary of defense who is coordinating with our allies to make sure that our troops are getting the kind of strategy and mission that they deserve,” the president said in an online chat sponsored by Google.

In the final minutes of the tally, Senate Majority Leader Harry Reid, D-Nev., switched his vote from “yes” to “no,” a procedural move that allows him to revive the nomination after the break. He set another vote for Feb. 26.

“Just when you thought things couldn’t get worse, it gets worse,” the Democratic leader lamented of the chamber’s bitter partisanship.

The successful Republican effort to block a vote on Hagel leaves one of the most contentious nominations of the Obama presidency in limbo, although Republicans signaled that they would relent and allow a simple majority vote on Hagel when they return from their recess.

Sen. Lamar Alexander, R-Tenn., voted against ending debate. But he said that he expects to change his vote, and he believes many of his GOP colleagues will do the same.

“I’m confident that after a reasonable period of time I’m going to vote to end the debate so that we can have an up-or-down vote on Chuck Hagel,” Alexander said. “I suspect there will be a large number of Republican senators who also do that.”

Echoing a complaint by other Republicans, Alexander called Thursday’s vote “unfortunate” and “unnecessary” because Hagel’s nomination came up on the Senate floor too quickly — just two days after it was approved by a bitterly divided Armed Services Committee.

Still, a week without any resolution and the possibility of any surprises are the last things any White House wants for its nominees. Hagel’s nomination has been unusual, facing a well-funded opposition that has unleashed a barrage of criticism in campaign-style television and print ads. Hagel has faced intense opposition from Republicans, who have challenged his past statements and votes on Israel, Iran, Iraq and nuclear weapons.

At least one group insisted shortly after the vote that it would redouble its efforts to defeat Obama’s choice.  

“The Emergency Committee for Israel will continue to work to convince a majority of senators of the undeniable truth that we can do much, much better than Mr. Hagel,” William Kristol, chairman of the group said in a statement.

The vote on Hagel combined with the delay on CIA Director-designate John Brennan’s nomination puts Republicans in a tough position as Democrats are certain to cast them as filibustering two critical members of the Obama’s second-term national security team.

“Today’s vote to filibuster Chuck Hagel’s nomination by Republicans is a disgrace, and the GOP is now holding America’s security and its troops hostage,” said Jon Soltz, an Iraq war veteran and chairman of VoteVets.org.

Republicans, led by Sens. John McCain and Lindsey Graham, had been blocking the confirmation of their former colleague until they received information from the White House on when Obama contacted Libyan officials after the attack on the U.S. mission in Benghazi last September in which Ambassador Chris Stevens and three other Americans were killed.

The White House responded to questions about Benghazi by saying former Secretary of State Hillary Clinton called Libyan President Mohamed Magariaf on Obama’s behalf on Sept. 11, the day of the attack, to coordinate additional support to protect Americans in Libya. White House counsel Kathryn Ruemmler said Obama spoke to Magariaf on the evening of Sept. 12.

The Obama administration also had disclosed the calls at the time they were made.

Reid said it was “shocking” and “tragic” that the GOP would attempt to block Hagel’s nomination at a time when the U.S. military is engaged in so many places around the world. “Not a single nominee for secretary of defense ever in the history of our country has been filibustered,” he said in a speech on the Senate floor.

In the nation’s history of hundreds of Cabinet nominees, the Senate has only rejected nine nominees and 21 were withdrawn or no action was taken, according to Senate historian Donald Ritchie. On just two occasions has the Senate imposed a 60-vote threshold for a Cabinet nominee. Neither was the president’s pick for defense secretary.

A full Senate vote on Hagel had been expected Friday after Reid filed a motion to limit debate. While Democrats hold a 55-45 edge in the Senate and have the numbers to confirm Hagel on a majority vote, they needed the support of five Republicans to clear the way for a majority vote. In the end, they only got four.

Graham had said Wednesday he would vote against ending debate on Hagel’s nomination.

“There seems to not be much interest to hold this president accountable for a national security breakdown that led to the first ambassador being killed in the line of duty in over 30 years,” Graham said. “No, the debate on Chuck Hagel is not over. It has not been serious. We don’t have the information we need. And I’m going to fight the idea of jamming somebody through until we get answers about what the president did personally when it came to the Benghazi debacle.”

The Senate Intelligence Committee is pushing off a vote on Brennan 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 of California said a vote likely will be postponed until late February.

The 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.

If ultimately confirmed by the Senate, Hagel, 66, would take charge of the U.S. armed forces at a time of turmoil. Automatic cuts to the Pentagon’s budget are looming, American troops in Afghanistan are being halved over the next year, North Korea has tested a nuclear weapon, Iran remains a threat in the Persian Gulf region, and Syria, Iraq, Libya, Egypt, Mali and Tunisia all are in a state of unrest.

At a Pentagon award ceremony on Thursday for Clinton, Panetta said it was fitting to recognize her accomplishments as secretary of state on Valentine’s Day. And he said the second-best Valentine’s Day present would be for the Senate to confirm Hagel and allow Panetta and his wife to “get the hell out of town.” He said he’s got his belongings packed.

Republicans accused Democrats of setting up a test vote Thursday that they knew would fail so the president’s allies could paint Republicans as obstructionists during the Presidents Day break.

“We could have worked this out,” said Republican Sen. John Cornyn of Texas.