WASHINGTON (Reuters) - U.S. phone companies would be shielded from potentially billions of dollars in lawsuits under an anti-terror spy measure that appears headed toward approval, congressional sources said on Wednesday.

A pilot talks on the phone at Reagan National Airport near Washington February 17, 2003. REUTERS/Brendan McDermid

House of Representatives Democratic Leader Steny Hoyer, a lead negotiator on the bill, said, “We’re very close to having an agreement,” and a House vote could come as early as Friday.

Democratic and Republican aides and a lobbyist familiar with negotiations said the House would likely approve the measure overwhelmingly. Despite opposition from its top two Democrats, the Senate would then likely give it final approval, clearing the way for President George W. Bush to sign it into law.

Bush has been pushing for retroactive immunity for any telephone company that participated in warrantless domestic surveillance program he began after the September 11 attacks.

One Democratic aide said the backers definitely seem to have the votes. Other Democratic and Republican aides, all speaking on condition of anonymity, agreed.

Senate Democratic Leader Harry Reid and Assistant Senate Democratic Leader Dick Durbin oppose immunizing telephone companies from lawsuits and voiced opposition this week to the proposal. “I will not support that, but a lot of people will,” Reid said on Tuesday.

Hoyer argued the bill would provide greater protection of civil liberties than one the Senate approved in February.

House Democratic leaders have refused to bring the Senate bill up for a vote in their chamber, forcing compromise talks.

The Senate bill would grant retroactive immunity to any phone company that participated in Bush’s spying program.

The proposed compromise would allow a federal district court to dismiss a suit if the company was provided written assurances that Bush authorized their participation in the spy program and that it was legal, sources said.

About 40 civil lawsuits have been filed accusing AT&T Inc, Verizon Communications Inc and Sprint Nextel Corp of violating Americans’ privacy rights in helping the domestic surveillance program.

Damages could total billions of dollars.

The White House and Democratic-led Congress have been trying for months to reach an agreement to modernize the 1978 Foreign Intelligence Surveillance Act, or FISA, which requires the government receive secret-court approval to conduct surveillance on foreign targets in the United States.

Critics charge Bush violated the law in authorizing warrantless surveillance. Bush maintains he had the wartime power to do it. He later put the program under FISA jurisdiction but its terms remain secret.

As part of any law to update FISA, Bush has demanded retroactive immunity for any telephone company that participated in his spying program.

Critics, including civil rights groups and many Democratic lawmakers, argue it should first be determined what the phone companies did before deciding whether to give them immunity.