In a crucial vote early Friday, the bill's supporters were not able to get the 60 votes needed to overcome a threatened filibuster by Democratic Senator Russ Feingold, Republican Larry Craig and their allies. The final vote was 52-47.
President Bush, Attorney General Alberto Gonzales and Republican congressional leaders had lobbied fiercely to make most of the expiring Patriot Act provisions permanent, and add new safeguards and expiration dates to the two most controversial parts: roving wiretaps and secret warrants for books, records and other items from businesses, hospitals and organisations such as libraries.
Feingold, Craig and other critics have called for the law to be extended in its present form so they can continue to try and add more civil liberties safeguards. But Bush, Senate Majority Leader Bill Frist and House Speaker Dennis Hastert have said they won't accept a short-term extension of the law.
If a compromise is not reached, the 16 Patriot Act provisions expire on December 31.
Frist changed his vote at the last moment after seeing the critics would win. He decided to vote with the prevailing side so he could call for a new vote at any time. He immediately objected to an offer of a short-term extension from Democrats, saying the House won't approve it and the president won't sign it.
"In the war on terror, we cannot afford to be without these vital tools for a single moment," White House press secretary Scott McClellan said. "The time for Democrats to stop standing in the way has come."
But the Patriot Act's critics got a boost from a New York Times report saying Bush authorised the National Security Agency to monitor the international phone calls and international e-mails of hundreds perhaps thousands of people inside the United States. Previously, the NSA typically limited its domestic surveillance to foreign embassies and missions and obtained court orders for such investigations.
"It is time to have some checks and balances in this country," said Democrat Senator Patrick Leahy, ranking Democrat on the Judiciary Committee. "We are more American for doing that."