If these provisions of the USA Patriot Act expire on December 31, as scheduled, the Republican-led Senate could take another crack at renewing them as soon as Congress begins a new year in January, aides said.

Democrats, who are using a procedural maneuver known as a filibuster to block renewal, have proposed a three-month extension to provide time to resolve differences. But the White House and Republican congressional leaders have rejected such a move.

"Those on the Senate floor who are filibustering the Patriot Act are killing the Patriot Act," said Senate Majority Leader Bill Frist, a Tennessee Republican.

Four of the 46 senators using the delaying tactic to thwart the USA Patriot Act renewal are members of Frist's party. It is a pesky, irritating fact for Republicans who are eager to portray the impasse as Democratic obstructionism, and a ready-made rejoinder for Democrats expecting campaign attacks on the issue in 2006 and 2008.

The four Republican rebels -- Larry E. Craig (Idaho), Chuck Hagel (Neb.), John E. Sununu (N.H.) and Lisa Murkowski (Alaska) -- have joined all but two Senate Democrats in arguing that more civil liberties safeguards need to be added to the proposed renewal of the Patriot Act. The law makes it easier for FBI agents to monitor phone calls, search homes and obtain business records of terrorism suspects. The four stand calmly at the center of a political storm that soon will determine whether the law, enacted soon after the 2001 terrorist attacks, is renewed in a modified form or allowed to expire in 11 days.

The act is a centerpiece of U.S. President George W. Bush's self-declared war on terrorism. Debate over renewing the provisions has escalated with revelations last week that Bush authorized spying without warrants on Americans suspected of having ties to terrorists.

Provisions up for renewal include ones involving wiretaps, access to business records and information-sharing by law enforcement and intelligence authorities.

The House of Representatives last week voted to renew the provisions, but that bill has been blocked in the Republican-led Senate.

Republican leaders have turned down a temporary extension, saying the proposed renewal would make improvements in civil liberties. Critics say the improvements are insufficient.

Senate Minority Leader Harry Reid, a Nevada Democrat, said, "The president says he wants to fight the terrorists, but his political stunt with the Patriot Act suggests he's more interested in scoring political points."

"Extend it, don't end it," said Reid. He said a majority of the Senate would back a temporary extension if Republican leaders allowed a vote on it.

Republicans aides noted that a majority of the Senate backs final congressional approval of the House-approved renewal.

A bid to end the procedural roadblock and move to passage of the measure fell eight votes short of the needed 60 in the 100-member Senate last week, with a few Republicans joining most Democrats in opposing it.

Frist said, "I've made it very clear where I stand. I'm opposed to opposed to (temporary) extensions."

"Why leadership on the other side would celebrate killing the Patriot Act, I don't understand it," Frist said.