[WASHINGTON] With a key law underpinning US bulk surveillance programmes set to expire, the future appears murky for the data sweep led by the National Security Agency.
At midnight on Sunday EST, barring a last-minute deal in Congress, a key section of the US Patriot Act - used as a legal basis for much NSA surveillance - will expire or "sunset." This would shut down most "bulk collection" efforts by US intelligence and law enforcement, programs which have sparked outrage since revelations from former NSA contractor Edward Snowden.
A senior administration official said bulk collection servers would be turned off at 4:00 pm (2000 GMT) and any collection after midnight would be deemed illegal.
The deadline has led to a frenzy of activity in Congress, seeking a way to keep programmes intact for national security investigations, but the outcome is far from clear.
Earlier this month the House of Representatives passed the USA Freedom Act to rein in NSA authority by ending bulk collection and improving transparency at a secret court which supervises the programme.
But the Senate blocked a vote on the bill and failed to muster enough support for a short-term extension of the law: Section 215 of the Patriot Act.
Some senators offered compromise measures, but it remains unclear if these can garner enough support in the Senate or prompt the House to reconsider its own measure.
Harley Geiger at the Center for Democracy & Technology, which has led a campaign for the USA Freedom Act, said the compromise bills are far weaker in reining in the surveillance.
Mr Geiger said that, if the law expires even for just one day, it may change the dynamic of the vote process because lawmakers would be reinstating surveillance authority and not simply extending existing programmes.
"Civil liberties groups are united in opposing anything weaker than the USA Freedom act," he said.
Members of the House have also warned that they may not accept a different measure from the Senate or extend the existing law.
"If the Senate chooses to allow these authorities to expire, they should do so knowing that sunset may be permanent," said a statement from leaders of the House Judiciary Committee.
Adding to the confusion is a US appeals court ruling which said the government went beyond the intent of Congress with bulk collection and that the program was illegal.
This means lawmakers must affirm they want a sweeping surveillance effort, which has been fiercely criticised at home and abroad.
Some civil liberties activists welcome the possibility of a "sunset," saying it is better than a weak reform.
"The Patriot Act, rushed through Congress in the wake of a national crisis, included sunset provisions for a reason: The extraordinary new powers created by the law were to be re-examined - and allowed to expire if abusive or ineffective. Both of those criteria have been met," said David Segal of the activist group Demand Progress, on behalf of a coalition including Tea Party Nation and the Council on American-Islamic Relations.
Mr Geiger said an expiration would be a mixed outcome and that a better result would be passage of the USA Freedom Act, even if the reforms are relatively modest.
"If we have a sunset, surveillance authority becomes much more narrow," he told AFP.
"But the downside is that a sunset will cause the intelligence agencies to freak out and security hawks in Congress to claim this is a national security crisis."
The White House is urging lawmakers to step up with an agreement before the expiration, to preserve the ability to keep key national security efforts in operation.
"I expect them to take action, and take action swiftly," President Barack Obama said on Friday.
"I don't want us to be in a situation in which for a certain period of time those authorities go away, and suddenly we're dark," he said.
"Heaven forbid we've got a problem where we could have prevented a terrorist attack or apprehended someone who is engaged in dangerous activity, but we didn't do so simply because of inaction in the Senate." James Clapper, director of national intelligence, said the intelligence community would "lose important capabilities." "For new investigations, we will no longer be able to get orders allowing us to effectively track terrorists and spies who switch communications devices," he said.
But Jameel Jaffer of the American Civil Liberties Union cautioned against "scaremongering" over the sunset.
"The government has many other tools that allow it to collect the same kinds of things that it can collect under Section 215," Mr Jaffer said on the Just Security blog.
He said expiration would be a political blow to the NSA, but "there's no support for the argument that the sunset of Section 215 would compromise national security."