The National Security Agency has begun winding down its collection and storage of American phone records after the Senate failed to agree on a path forward to change or extend the once-secret program ahead of its expiration at the end of the month.
Barring an 11th hour compromise when the Senate returns to session on May 31, a much-debated provision of the counter-terrorism Patriot Act and some other lesser known surveillance tools will sunset at midnight that day.
The change also would have a major impact on the FBI, which uses the Patriot Act and the other provisions to gather records in investigations of suspected spies and terrorists.
In a chaotic scene during the early morning hours on Saturday, Senate Republicans blocked a House bill known as the USA Freedom Act, which would have ended the NSA's bulk collection but preserved its ability to search the records held by the phone companies on a case-by-case basis.
The bill was backed by President Barack Obama, House Republicans and the nation's top law enforcement and intelligence officials.
It fell just three votes short of the 60 needed for passage. All the "no" votes but one were cast by Republicans, some of whom said they thought the USA Freedom Act didn't go far enough to help the NSA maintain its capabilities.
If Senate Republican leaders were counting on extending the current law and continuing the negotiations, they miscalculated. Democrats and libertarian-minded Republicans refused to go along.
A bill to grant a two-month extension of the law failed, and senators objected to each attempt by Majority Leader Mitch McConnell of Kentucky to offer up a short term extension.
The failure to act means the NSA will immediately begin curtailing its searches of domestic phone records for connections to international terrorists.
The Justice Department said in a statement that it will take time to taper off the collection process from the phone companies.
That process began Friday, said an administration official who would not be identified because he was not authorized to discuss the matter publicly.
While the phone records program has never been credited with thwarting a terrorist plot, the Senate failure also imperils other tools that the FBI has been using to hunt for suspected spies and terrorists.
The FBI uses Section 215 of the Patriot Act to gather financial and other types of records in national security cases.
Another expiring provision makes it easier for the bureau to track "lone wolf" terrorism suspects who have no connection to a foreign power, and another allows the government to eavesdrop on suspects who continuously discard their cellphones in an effort to avoid surveillance.
