President Bush is expected to sign the extension into law swiftly

Provisions set to expire on Friday were extended until 10 March, to give negotiators more time to reach a deal to make the anti-terror act permanent.

Democrats, and some Republicans, want greater protection of civil liberties.

Introduced after the 9/11 attacks, the act gives the government more powers to monitor terror suspects. George W Bush is expected to sign it into law.

Sixteen provisions of the law were originally due to expire on 31 December 2005, but Congress then extended them until 3 February.

The latest five-week extension was passed by the Senate on Thursday, a day after it had been approved by the House of Representatives.

Senator Larry Craig, one of the Republicans demanding more safeguards, said negotiations with the White House were continuing and an agreement was expected soon.

Judiciary Committee Chairman Arlen Specter said: "We need the Patriot Act. I'm prepared to work on it further to improve it."