To guard against the expiration of a temporary surveillance law Feb. 16, Senate Majority Leader Harry Reid , D-Nev., has filed a bill that would extend it for 15 days.

The Senate is expected to pass a six-year bill overhauling the Foreign Intelligence Surveillance Act on Feb. 12, but that gives lawmakers little time to work out a compromise between the Senate bill and a House-passed version before the Presidents Day recess begins and the temporary law expires.

Reid filed the latest extension Friday “in case we can’t finish the conference negotiations in time,” spokesman Jim Manley said.

Democrats had pressed for a 30-day extension of the current law when it was on the verge of expiring Feb. 1, but President Bush rejected the notion, eventually supporting a 15-day extension instead.

Bush has said he will not accept another extension of the law.

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The expiring law allows the executive branch to conduct surveillance of foreign targets without a warrant, even when that foreign target is communicating with someone in the United States. The secret court created by the Foreign Intelligence Surveillance Act has limited authority to approve some of the procedures used to conduct such spying.

The pending Senate overhaul would strengthen the FISA court’s authority to approve those procedures. It also would grant retroactive legal immunity to companies being sued for their alleged cooperation in the administration’s warrantless surveillance program.

The House bill would place more restrictions on the government’s spying powers and would not grant retroactive immunity. House and Senate aides began negotiating this week over a final version, in anticipation of the Senate bill’s passage.

House Intelligence Chairman Silvestre Reyes , D-Texas, said Thursday that the topic of immunity has not been discussed yet because key House members only recently received access to legal documents from the administration that selected senators saw last year.