WASHINGTON - With key post-9/11 surveillance authorities lapsed, the US Senate votes Tuesday on reforms that would end the government's most controversial spy programme, but altering the legislation would put its fate in jeopardy.
The USA Freedom Act, supported by the White House, passed the House of Representatives with broad bipartisan support in May.
The Senate, which is now debating the bill, could pass up to three amendments Tuesday that were introduced by Senate Majority Leader Mitch McConnell, and House leaders warned the upper chamber that the changes could doom the measure.
"The House is not likely to accept the changes proposed by Senator McConnell," House Judiciary Committee chairman Bob Goodlatte said in a statement with the panel's top Democrat John Conyers.
That would mean key spy provisions could expire for good.
The Senate met in a rare Sunday session to try to pass the Freedom Act, which would prevent the lapse of roving wiretap and lone-wolf tracking powers.
But with Senator Rand Paul, a Republican presidential candidate, slow-walking the process, the bill failed to cross the finish line by the midnight deadline for reauthorization of the programs.
Lawmakers insist it is crucial to pass the reform bill swiftly, to help make America's counterterrorism toolbox fully usable.
"We need to work quickly to remedy this situation," McConnell said Monday on the Senate floor.
He announced a procedural vote for 10:30 am (1430 GMT) Tuesday, and a final vote is likely to occur that afternoon.
"Most people want to get this done," a senior Republican aide told AFP.
Changes could doom bill
But if any of McConnell's amendments pass, the bill bounces back to the House for approval of the changes before it goes to President Barack Obama's desk for his signature.
That might be a heavy lift, House leaders warn.
"The best thing to do would be to pass our bill," McCarthy told reporters, according to The Washington Examiner. He declined to comment on the amendments or say whether they had a shot at passing the House.
Several lawmakers have insisted the amendments water down the original Freedom Act and could lead dozens of supporters to oppose it.
The changes include extending from six months to one year the transition period for switching from the National Security Agency storing the metadata on millions of Americans to relying on warrants to obtain specific information from the telecommunications companies.
Another amendment would require the director of national intelligence to review the system.
"These amendments only serve to weaken the House-passed bill and postpone timely enactment of legislation that responsibly protects national security while enhancing civil liberty protections," Goodlatte and Conyers wrote.
Senate Intelligence Committee chairman Richard Burr, sponsor of one of the amendments, remained hopeful that the House will accept the changes, if passed by the Senate.
"I hope by tomorrow afternoon we can have this completed, and that we can send it to the House, and by the time we go to bed tomorrow night this might all be back into place," he said.
The Freedom Act, however, would ensure that indiscriminate bulk collection of telephone records would cease.