US Senate Republicans ignored a White House demand for a vote to confirm President Barack Obama's pick for defense chief, throwing up a roadblock at a time of rising national security tensions.
Democrats fell one vote short of overcoming the procedural delay and clearing the way for final consideration of Chuck Hagel. Republicans had sought more time to receive and study responses to questions that they said remained unanswered.
The delay means the confirmation vote for Hagel, a former Republican senator, will most likely happen some 10 days from now after a one-week Senate recess.
Obama called the move "unfortunate," while furious Senate Democrats insisted their rivals were more concerned with political point-scoring than ensuring the defense department was adequately represented.
Democratic Majority Leader Harry Reid took to the floor immediately after the vote to rail against the move, which he saw as "embarrassing the president" at a time of strain in the Middle East, ongoing war in Afghanistan and North Korea recently testing a nuclear device.
In a separate statement, Reid expressed bafflement about what he described as "one of the saddest spectacles I have witnessed in my 27 years in the Senate."
The defeat does not doom Hagel's nomination to lead the Pentagon in Obama's second term, and Reid has already said he would call another procedural vote on February 26, the first working day after next week's break.
"I think we all need to take a deep breath," a White House official said on condition of anonymity.
"Senator Hagel is going to be confirmed, if not tomorrow then when the Senate returns from recess."
Before allowing a vote, Republicans had demanded more information on Hagel's finances and on Obama's role in responding to an attack on the US consulate in Benghazi, Libya last year.
Reid responded by trying to force a vote on the nomination. With Democrats holding a 55-45 edge in the Senate, he needed five Republicans to get to the 60 votes needed to overcome the blocking tactics. He got just four.
Without such a filibuster, presidential nominations require a simple majority of senators in the 100-seat chamber -- a barrier Hagel is virtually assured of surpassing.
Obama said it was the first time ever that a defense secretary nominee was filibustered.
But in a "Google fireside hangout" filmed at the White House, he said "my expectation and hope is that Chuck Hagel, who richly deserves to get a vote on the floor of the Senate, will be confirmed as our defense secretary."
The delay could cause allies to worry.
"It's just kind of unfortunate that this kind of politics intrudes at a time when I am still presiding over a war in Afghanistan and I need a secretary of defense who is coordinating with our allies to make sure our troops are getting the kind of strategy and mission that they deserve," Obama said.
The White House said Hagel had been expected to appear at a NATO ministerial meeting next week in Brussels to discuss the pull-out from Afghanistan.
Outgoing Defense Secretary Leon Panetta had already announced plans to leave Washington and return to California, but Pentagon spokesman George Little said Panetta "will attend the NATO Ministerial in Brussels next week and will continue to carry out his duties as secretary of defense."
Reid accused Republicans of acting like children over Hagel, saying it was "shocking" they would do so while the United States was at war.
Hagel's hope to eventually overcome the filibuster later this month appear to rest with his one-time friend and colleague Senator John McCain, who eviscerated him in a confirmation hearing and voted Thursday for the delay.
McCain and his fellow Republican hawk Senator Lindsey Graham both said they would drop the delaying tactics after the break.
Both men 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 Americans.
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.
Several Republicans have taken issue with Hagel's public stances in recent years on Iran, nuclear weapons, Israel and the US.