By Patricia Zengerle and Roberta Rampton
WASHINGTON (Reuters) - U.S. President Barack Obama warned on Friday that surveillance powers used to prevent attacks on Americans could lapse at midnight on Sunday unless "a handful of senators" stop standing in the way of reform legislation.
Obama said he had told Republican Senate Majority Leader Mitch McConnell and other senators that he expects them to act swiftly on a bill passed by the House of Representatives that would renew certain powers and reform the bulk collection of telephone data.
"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 and heaven forbid we've got a problem," Obama told reporters in the Oval Office.
McConnell has called the Senate back to Washington for a rare Sunday session to deal with the expiration of three provisions of the Patriot Act, including Section 215, used to justify the National Security Agency's collection of billions of Americans' telephone call records.
The NSA program has worried privacy advocates since it was exposed to journalists two years ago by former NSA contractor Edward Snowden, now a fugitive in Russia.
On Friday, online activists blocked congressional offices' access to thousands of websites to protest the Patriot Act.
Republicans, who control both the Senate and House, have been unable to agree on how to deal with the expiration. Late last week, the Senate failed by three votes to advance the USA Freedom Act, the reform bill backed by Obama and passed overwhelmingly by the House.
A senior Republican leadership aide said late on Friday that the party's leaders in the House wanted the Senate to take up and pass the Freedom Act.
The Freedom Act would end the bulk collection of telephone records and replace it with a more targeted system for retrieving the information.
In the Senate, the measure is supported by Democrats, but opposed by Republican security hawks, who want to extend the Patriot Act provisions, and libertarian-leaning Senator Rand Paul, a 2016 Republican presidential candidate.
Paul and other privacy advocates have blocked Senate efforts to pass any extension.
Congressional aides said backers might be able to win the additional three Senate votes to advance the Freedom Act, possibly by allowing opponents to offer amendments.