Senate Republicans rose to the defense of the National Security Agency on Tuesday by filibustering a bill that would have halted the agencys phone-snooping program, saying it is now more critical than ever amid advancing terrorism in the Middle East and fears of homegrown terrorism in the U.S.

The vote, in which 41 Republicans and one Democrat banded together for the filibuster, leaves the most controversial part of the Patriot Act in place.

It also ends efforts to rein in the NSA program for the foreseeable future because Republicans will take control of the chamber early next year and are unlikely to revisit the issue.

This is the worst possible time to be tying our hands behind our backs, said Senate Republican leader Mitch McConnell, who pointed to the advance of Islamic State terrorists in Iraq and Syria. The threat from ISIL is real. Its different from what weve faced before. And if were going to overcome it if our aim is to degrade and destroy ISIL, as the president has said then thats going to require smart policies and firm determination.

Pressure will now build on President Obama to make changes on his own. He has put some limits on the NSA, but asked Congress for guidance and said he strongly supported the legislation the Republicans defeated.

Still, the NSAs snooping days may be numbered. The controversial sections of the Patriot Act are up for renewal next year, and unless Congress can reach an agreement, those powers will expire.

Tuesdays vote was a blow for privacy advocates, who won overwhelming support in the House this year for a bill that dramatically curtailed NSA snooping and other bulk-records collection by the government.

The advocates tried to build a similar conservative-liberal coalition in the Senate, but most Republicans balked.

Tonight, Senate Republicans have failed to answer the call of the American people who elected them, and all of us, to stand up and to work across the aisle, said Judiciary Committee Chairman Patrick J. Leahy, the Vermont Democrat who pressed for the vote, fearing GOP infighting would doom chances for a bill next year.

Mr. Leahy accused Republicans of scare tactics to try to preserve the Patriot Act authority.

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NSA phone snooping upheld by Senate Republicans' filibuster