Senate Majority Leader Mitch McConnell on Capitol Hill on May 19, 2015. (Michael Reynolds/European Pressphoto Agency)

A bitter ideological divide in Congress appeared destined Wednesday to at least temporarily end the bulk collection of Americans’ phone records as government officials warned they would have to begin shuttering the program after Friday if lawmakers do not act.

In a memorandum, the Justice Department said the National Security Agency would need to act “to ensure that it does not engage in any unauthorized collection” or use of the data should the program not be extended before a June 1 deadline.

The memo, along with comments Wednesday by FBI Director James B. Comey, puts pressure on lawmakers to act at a time when congressional Republicans remain divided over the NSA’s controversial gathering of private telephone records for counterterrorism purposes.

The House last week overwhelmingly passed a bill that would sharply limit the record-gathering, with nearly 200 Republican votes. But Senate Majority Leader Mitch McConnell (R-Ky.) favors a long-term continuation of the existing phone-data collection program and has suggested that the House bill will not gain enough votes to move forward in the Senate.

Sen. Rand Paul (R-Ky.) took to the floor Wednesday afternoon to speak against the renewal of the Patriot Act. Paul claims it gives government too much access to citizens’ private data. (C-SPAN)

He instead raised the possibility of a short-term extension of the current authority under the Patriot Act’s Section 215.

“What I think is the most important thing is to make sure we still have a program, a program that works, and helps protect the American people from attacks,” McConnell said Tuesday. “That’s the bottom line here. And we’re going to work toward addressing that this week, and we’ll see how it turns out.”

But House Republican leaders have said they have no plans to bring a short-term extension to a vote before leaving for a week-long recess Thursday, effectively foreclosing any temporary fix. And there is strident opposition from some senators to an extension of any length.

Sen. Rand Paul (R-Ky.), who is running for president, took to the Senate floor Wednesday afternoon to begin what he told his political supporters would be a filibuster of attempts to extend current law.

“I, for one, say there needs to be a thorough debate, a thorough and complete debate, over whether we need to allow our government to collect all of our phone records all of the time,” Paul said at the outset of his remarks, which continued into Wednesday evening.

Paul’s marathon speech raised the possibility that the Senate will not be able to vote on surveillance legislation until Saturday, well after House members leave town. If senators pass the House bill, the USA Freedom Act, there will be no lapse in collection. Otherwise there will almost certainly be a lapse, because the House is not set to meet again until June 1 — hours after the current authority would expire.

Some Senate Republican leaders suggested the House could take up a short-term extension when it returns. But the Justice Department made clear that the government needs to know Congress’s intentions this week.

The current court order authorizing the program requires the government to file for any renewal no later than Friday if it intends to continue the collection, according to the memo, which was obtained by The Washington Post. After that, the memo says, “it will become increasingly difficult for the government to avoid a lapse in the current NSA program of at least some duration.”

It added, “In the event of a lapse in authority and subsequent reauthorization, there will necessarily be some time needed to restart the program.”

Meanwhile, Comey warned the June 1 “sunset” affects not only the NSA’s bulk collection but also three legal tools that he said are “critical” to the bureau’s investigations of terrorists and spies. They are “noncontroversial,” he said, and are getting drowned out by the focus on the NSA program.

Section 215 not only authorizes the contested bulk phone records collection but also enables the FBI to obtain a court order for data on individual suspects, Comey said.

“If we lose that authority . . . that is a big problem,” he said Wednesday at Georgetown University Law Center. “We’ll find ourselves in circumstances where we can’t” obtain records with a grand jury subpoena or a national security letter in counterterrorism or counterespionage probes, he said.

Two other provisions that are set to lapse enable surveillance of “lone wolf” suspects who are not linked to any foreign terrorist group or foreign government and allow “roving wiretaps” on targets who frequently switch communications devices.

Democrats and at least one GOP senator urged McConnell and like-minded Republicans to drop their opposition to the House bill, calling it a carefully crafted compromise that has won endorsements across the political and ideological spectrum.

Sen. Charles E. Schumer (D-N.Y.), the third-ranking Democratic leader, said the USA Freedom Act represented a “lifeboat” for Republicans who fear a sunset of the current law.

On the Senate floor Tuesday afternoon, Sen. Mike Lee (R-Utah) noted that the bill had the support of most House Republicans, Attorney General Loretta E. Lynch, Director of National Intelligence James R. Clapper Jr. and an ideologically diverse coalition of outside groups including the NAACP and the National Rifle Association.

“This is a supermajority,” Lee said, “a super-duper-majority.”

But key Republican senators continue to have concerns about the revisions set out in the House bill, which would end the NSA’s mass collection of phone-call metadata. That information, which includes dialed numbers, call times and durations of calls, would remain in the hands of phone companies. The government would then have to obtain a court order to compel the companies to send records on specific terrorism suspects to the NSA.

Sen. Richard Burr (R-N.C.), chairman of the Senate Intelligence Committee, said earlier this week that he was seeking further assurances that the system set out in the House bill would be workable for intelligence agencies.

“I’m trying to make sure we’ve got a viable way forward that protects the capabilities that this program provides but allows Mike Lee and others the certainty that it’s going to transition out of a bulk storage program at some point in the future,” he said.

Such a compromise, said Senate Majority Whip John Cornyn (R-Tex.), might involve “a longer period of transition where we can actually verify it works and not just do it based on a hope and prayer.”

Lee, a lead Senate sponsor of the USA Freedom Act, said he was open to the idea of a compromise to extend the transition period. “I don’t think there’s anything particularly sacrosanct about the six months,” he said. “I don’t have a problem with someone suggesting a longer term if they can demonstrate that’s necessary.’’

Intelligence officials say the loss of the data-gathering power would be a blow. “You’re taking tools off the table while [the Islamic State] is taking over Ramadi,” a U.S. official said. “They’ve got to take ownership of that.”

A lapse of even a day or two would be highly disruptive to ongoing investigations, officials said. If a court order expired during a gap in authority, for instance, it could not be renewed, and preemptively renewing those orders can be time-consuming.

“It would screw things up,” said the U.S. official, who spoke on the condition of anonymity because he was not authorized to comment openly to reporters.

The government’s bulk data collection was not publicly known until the disclosures by former NSA contractor Edward Snowden in 2013. To justify the surveillance dragnet, the federal authorities relied on the Patriot Act, which Congress passed after the Sept. 11, 2001, terrorist attacks.

Some privacy and transparency groups say that losing Section 215 would not cripple investigations, because the government would still have its predecessor — a pre-Patriot Act provision that would allow it to collect a narrower class of business records if they pertain to foreign powers or agents of foreign powers.

“It’s time for the national security establishment to argue why they need enhanced powers . . . after 14 years of the Patriot Act being in place,” said David Segal, executive director of Demand Progress, a grass-roots civil liberties group.

Sen. Martin Heinrich (D-N.M.), who has vowed to filibuster any extension of the current law, said he doubts that McConnell has the 60 votes needed to advance a short-term fix, citing widespread opposition among Democrats. “It takes our eye off the ball here in terms of getting a long-term solution,” he said. “Why would we extend even for a short period of time a law that has been ruled illegal by the courts?”

A federal appeals court ruled this month that Section 215 of the Patriot Act did not provide sufficient authority for the bulk surveillance program, but it stayed its ruling pending congressional action on the reauthorization of the law.