The US Senate rejected legislation early Saturday aimed at reforming NSA intelligence gathering, a blow to President Barack Obama and others who support ending the bulk collection of Americans' telephone records.
Senators also rejected efforts to extend the USA Patriot Act, increasing the prospects that the legal underpinnings of the domestic surveillance program will expire by June 1.
The House of Representatives passed the reform measure overwhelmingly last week, with Democrats and Republicans uniting in their desire to rein in the National Security Agency's highly controversial program that scoops up data from millions of Americans who have no connection to terrorism.
But it got hung up in the Senate, where it failed 57-42, shy of the 60 necessary to advance in the chamber.
Three provisions -- the telephone dragnet, roving wiretaps and lone-wolf tracking -- are set to expire at the end of the month.
With no reforms in place, and a lapse in national security operations looming, Senate leaders sought to temporarily reauthorize the Patriot Act which governs such intelligence operations.
But several extensions offered by Senate Majority Leader Mitch McConnell were rejected, triggering an extraordinary scramble for an overnight solution on the Senate floor before lawmakers were to go on a scheduled one-week break.
McConnell said the Senate could come back into session a day early, Sunday, May 31, in order to prevent a lapse in crucial national security operations.
"We're left with this option only," a chastened McConnell told colleagues at about 1:30 am (0530 GMT), after lawmakers rejected a two-month extension and several shorter options.
"We'll have a week to discuss it. We'll have one day to do it. But we better be ready next Sunday afternoon to prevent the country from being in danger by the total expiration of the program that we're all familiar with."
On Friday the White House drove home the very real prospect that vital intelligence elements could lapse on June 1.
"There is no plan B," White House spokesperson Joshua Earnest told reporters.
"These are authorities that Congress must legislate (and are) critically important to ensuring that the basic safety and security of the American people is protected, and that the basic civil liberties of the American people are protected."
McConnell's extension offers were rejected in part by Senator Rand Paul, a Republican 2016 presidential candidate who has long demanded an end to the telephone data dragnet.
"Our forefathers would be aghast" at the level of surveillance of Americans today, Paul said.
"This is a debate that should be had."
Paul, a vocal defender of personal liberties, had staged a 10-hour protest Wednesday on the Senate floor against re-authorizing bulk data collection.
Paul also voted against the reform bill, known as the USA Freedom Act.
The executive director of the Demand Progress activist coalition, David Segal, hailed the moved as "victory for democracy over totalitarianism."
"Those who helm the government's surveillance apparatus have engaged in craven abuse of already overly-expansive spying powers that do nothing to reduce the threat of terrorism, but pose ongoing threats to privacy, freedom, and democratic governance," he said.
But the Senate Intelligence Committee's top Democrat, Dianne Feinstein, backed the reforms, saying she opposed a compromise that was being crafted by the panel's chairman, Republican Senator Richard Burr.
"For those who want reform and want to prevent the government from holding the data, the Freedom Act is the only way to do it," she said, noting the measure has Obama's support.
"I think not to pass that bill is really to throw the whole program, that whole section 215... into serious legal jeopardy."
Kevin Bankston, policy director of New America's Open Technology Institute think tank, said blocking the measure was an "insult."
"It is a shocking insult to the democratic process, and to the American people who have been demanding reform for two years, that the Senate's leaders have ignored the White House, federal judges, and an overwhelming majority of the House of Representatives by blocking the USA Freedom Act," Bankston said.
Lawmakers and aides have noted that even if the Senate meets May 31 and approves an extension, the intelligence provisions would lapse, at least for a few hours, because the House would not come into session until later June 1 to vote on the Senate measure.