House and Senate Republicans were locked in an escalating standoff Friday over legislation reining in the National Security Agency, with lawmakers warning surveillance programs could "go dark" in a matter of days if they don't reach an agreement.

The standoff concerns a pair of dueling bills.

With Patriot Act authorization for NSA data collection set to expire on June 1, Senate Republican Leader Mitch McConnell is pushing a two-month extension to keep the programs running. But the House already has passed a separate bill, called the USA Freedom Act, that would end the NSA's bulk collection of domestic phone metadata, while replacing it with case-by-case searches, and extend two other expiring surveillance provisions used by the FBI.

The House has since left town for the holiday break, and House lawmakers are putting heavy pressure on the Senate to just accept their bill -- or else.

"The NSA programs will lapse if the Senate doesn't take our bill," a senior House GOP source told Fox News.

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    The administration is warning the NSA's bulk collection program could start winding down as early as this weekend without a new bill.

    House lawmakers have leverage because if the Senate goes with McConnell's two-month extension, and not the House-passed version, sources say the House would not come back in session to deal with it before June 1. That would leave an unfinished bill hanging on Capitol Hill over the holiday.

    In that case, one source told Fox News, "Those [NSA] programs will go dark."

    But Senate lawmakers could make the same dare.

    As early as Friday night, the Senate was looking to hold test votes on the dueling bills. But Senate Majority Whip John Cornyn, R-Texas, suggested that if they fail, the Senate could try passing a very short-term extension and toss it back to the House.

    Cornyn predicted the House would not let those programs expire -- despite insistence by House sources to the contrary.

    The president and his top law enforcement officials also are urging the Senate to pass the House bill. Officials say they will lose valuable surveillance tools if an agreement is not reached.

    But McConnell on Friday pushed back on that bill, saying the administration "could not guarantee whether a new system would work as well as the current system." He said the House and administration are relying on a "non-existent system" and questioned whether it could be built up efficiently.

    Sen. Richard Burr, chairman of the Senate intelligence committee, also floated an alternative plan that would essentially dare the House to reject it, allowing the legal authorities to expire.

    "I don't think anyone in the House wants it to go dead," he told reporters.

    Burr predicted the House's USA Freedom Act would fail to break the 60-vote threshold needed to end debate in the Senate, and he envisioned the same fate for a two-month extension of current law proposed by Senate leaders. As a compromise, he proposes that the Senate vote to extend current law between five days and a month.

    Alongside that, he said, he would introduce a bill to end NSA's bulk collection of phone records after a two-year transition period, up from six months in the House bill.

    The Senate would then depart, leaving it up to the House to take or leave the Senate proposal when House members return June 1.

    But both Obama administration officials and House sources indicate surveillance programs will indeed be in danger if the Senate doesn't pass the USA Freedom Act.

    The Department of Justice told lawmakers in a memo earlier this week that they would have to begin ramping down the NSA bulk collection this weekend -- even before the June 1 deadline -- if they didn't think Congress would renew them. The DOJ also said it would take a while to restart those programs if Congress did approve an extension after the fact.

    A senior House Republican aide told Fox News that the GOP leadership does not view that as an idle threat.

    In a conference call with reporters, senior Obama administration officials were adamant that if the Senate failed to pass the USA Freedom Act, the phone records program and other counterterrorism surveillance would be in jeopardy.

    Earlier Thursday, House Speaker John Boehner, R-Ohio, and Democratic leader Nancy Pelosi of California appealed for Senate consideration of the USA Freedom Act, which their chamber passed 338-88 last week.

    That bill would end the NSA's collection and storage of domestic calling records after a 180-day transition period. But it would preserve the agency's ability to query phone company records in search of domestic connections to international terrorists. The House measure also would renew two unrelated surveillance powers commonly used by the FBI to track spies and terrorists.

    Fox News Chad Pergram and The Associated Press contributed to this report.