Washington: Crucial national security provisions appeared likely to expire midnight Sunday as Senator Rand Paul vowed to block any last-minute votes to extend or reform the controversial program that collects telephone data on Americans.
Key parts of the USA Patriot Act which underpins domestic National Security Agency surveillance measures, including the bulk data dragnet, will "sunset" at the end of May 31 without action by lawmakers.
The House passed a bill reforming surveillance provisions and ending the program that compels US telephone companies to hand over to the government information on millions of Americans who have no connection to terrorism.
The Senate has yet to act, and with time running out, Majority Leader Mitch McConnell ordered senators back to the Capitol for a rare Sunday session to thrash out a solution.
But Paul, a 2016 presidential candidate staunchly opposed to the NSA bulk data program, threw a spanner in the works, insisting he will block any votes on the reform bill or an extension of the Patriot Act.
"Tomorrow I will force the expiration of the NSA illegal spy program," Paul posted Saturday on Twitter.
The impasse makes it increasingly likely that certain security provisions -- including roving wiretaps of terror suspects and lone-wolf tracking -- will lapse come Monday.
"These tools are not controversial," President Barack Obama, who supports the House`s reform bill, said Saturday in a radio address.
"But if Congress doesn`t act by tomorrow at midnight, these tools go away as well."
While he did not single out Paul by name, the president telegraphed his displeasure at the first-term senator`s obstructionist position, saying that "unfortunately, some folks are trying to use this debate to score political points."
"But this shouldn`t and can`t be about politics," Obama added. "Terrorists like Al-Qaeda and ISIL (the self-declared Islamic State group) aren`t suddenly going to stop plotting against us at midnight tomorrow."
It appeared increasingly likely, however, that the provisions will lapse, if only for a matter of hours or days.
If Paul blocks votes, as he has the right to do under Senate rules, the chamber would not be able to approve either the House reform bill or a Patriot Act extension until later in the week.
"Senator McConnell`s favorite tactic is to manufacture unnecessary crises and hope something gets worked out at the last minute," said Adam Jentleson, senior aide to Senate Minority Leader Harry Reid.
"We are watching Senator McConnell`s reckless, half-baked approach backfire badly before our eyes, with potentially devastating consequences for the American people."
A senior administration official said switches would be turned off for the bulk collection servers beginning at 3:59 pm (1959 GMT) Sunday, and any collection after midnight would be deemed illegal, without congressional authorization.