The Senate struggled to prevent an interruption in critical government surveillance programs early Saturday, rejecting both a House-passed bill and a short-term extension of the USA Patriot Act.
The back-to-back votes left lawmakers without a clear fallback, although current law doesn't expire until midnight May 31.
The White House has pressured the Senate to back the House bill, which would end the National Security Agency's bulk collection of domestic phone records. Instead, the records would remain with telephone companies subject to a case-by-case review.
The vote was 57-42, short of the 60-vote threshold to move ahead.
That was immediately followed by rejection of a two-month extension to the existing programs. The vote was 45-54, again short of the 60-vote threshold.
Republican officials said Senate Majority Leader Mitch McConnell, R-Ky., intended to try again, this time with an even shorter renewal of current law.
Whatever the Senate approves must be passed by the House, which has already left Washington for a weeklong Memorial Day break.
Complicating McConnell's efforts was an attempt by fellow Kentuckian Sen. Rand Paul, who has vowed to do everything he can to prevent the renewal of the bulk phone records collection.
"My filibuster continues to end NSA illegal spying," tweeted the Republican presidential contender.
The legal provisions authorizing the programs will expire at midnight May 31, and officials say they will lose valuable surveillance tools if the Senate fails to go along with the House. But key Republican senators oppose the House approach.
At issue is a section of the Patriot Act, Section 215, used by the government to justify secretly collecting the "to and from" information about nearly every American landline telephone call. For technical and bureaucratic reasons, the program was not collecting a large chunk of mobile calling records, which made it less effective as fewer people continued to use landlines.
When former NSA contractor Edward Snowden revealed the program in 2013, many Americans were outraged that NSA had their calling records. President Barack Obama ultimately announced a plan similar to the USA Freedom Act and asked Congress to pass it. He said the plan would preserve the NSA's ability to hunt for domestic connections to international plots without having an intelligence agency hold millions of Americans' private records.
Since it gave the government extraordinary powers, Section 215 of the Patriot Act was designed to expire at midnight on May 31 unless Congress renews it.
Under the USA Freedom Act, the government would transition over six months to a system under which it queries the phone companies with known terrorists' numbers to get back a list of numbers that had been in touch with a terrorist number.
But if Section 215 expires without replacement, the government would lack the blanket authority to conduct those searches. There would be legal methods to hunt for connections in U.S. phone records to terrorists, said current and former U.S. officials who spoke on condition of anonymity because they were not authorized to discuss the matter publicly. But those methods would not be applicable in every case.
The Justice Department has said the NSA would begin winding down its collection of domestic calling records this week if the Senate fails to act because the collection takes time to halt.