WASHINGTON (Reuters) - Facebook Inc FB.O, Alphabet Inc's Google GOOGL.O, Apple Inc AAPL.O and other major technology firms are largely absent from a debate over the renewal of a broad U.S. internet surveillance law, weakening prospects for privacy reforms that would further protect customer data, according to sources familiar with the matter.

FILE PHOTO - Protesters hold up signs in the audience section before a U.S. House Intelligence Committee hearing on the potential changes to the foreign intellience surveillance act (FISA) on Capitol Hill in Washington, DC, U.S. on October 29, 2013. REUTERS/Jason Reed/File Photo

While tech companies often lobby Washington on privacy issues, the major firms have been hesitant to enter a fray over a controversial portion of the Foreign Intelligence Surveillance Act (FISA), industry lobbyists, congressional aides and civil liberties advocates said.

Among their concerns is that doing so could jeopardize a trans-Atlantic data transfer pact underpinning billions of dollars in trade in digital services, the sources said.

Technology companies and privacy groups have for years complained about the part of FISA known as Section 702 that allows the U.S. National Security Agency (NSA) to collect and analyze emails and other digital communications of foreigners living overseas. Though targeted at foreigners, the surveillance also collects data on an unknown number of Americans - some privacy advocates have suggested it could be millions - without a search warrant.

Section 702 will expire at the end of the year unless the Republican-controlled Congress votes to reauthorize it. The White House, U.S. intelligence agencies and many Republican senators want to renew the law, which they consider vital to national security, without changes and make it permanent.

A coalition of Democrats and libertarian-leaning conservatives prefer, however, to amend the law with more privacy safeguards.

Reform Government Surveillance, a coalition of tech firms established after the 2013 leaks by former NSA contractor Edward Snowden, said reforming the law remains a priority. A spokeswoman declined to comment further but referred to two letters sent earlier this year by technology companies urging Congress to consider changes to the law.

Snowden exposed the spy agency’s program that collected U.S. phone call metadata in bulk and also the extent of spying under Section 702, embarrassing some U.S. technology firms.

The companies, working with privacy rights activists, successfully lobbied Congress two years ago to pass legislation that curtailed the NSA’s bulk collection of call records. For example, Facebook chief executive Mark Zuckerberg wrote on his Facebook page that he had personally called then-President Barack Obama to express “frustration over the damage the government is creating for all of our future.”

Now, however, Silicon Valley’s reduced involvement frustrates civil liberties groups because of a widely held view that Section 702 poses a far greater threat to privacy than the telephone program, which did not harvest actual content.

Facebook declined comment. Google and Apple did not respond to requests for comment.

PRIVACY SHIELD AGREEMENT

The companies’ relative inactivity is explained by several legal challenges in Europe to an agreement between the United States and the European Union, known as the Privacy Shield, the sources said. The litigation hinges on whether U.S. surveillance practices afford enough privacy safeguards. A coalition of human rights organizations has urged Europe to suspend Privacy Shield unless Section 702 is substantially reformed.

U.S. technology companies have privately bristled at those efforts, three industry lobbyists said, in part because expectations that 702 reforms will pass Congress are low.

“If you link them and you lose one, you lose both,” said one of the lobbyists, who like the others requested anonymity to discuss private conversations with technology companies.

The lobbyist added that several major firms were more interested in making deals with the Trump administration that could affect their bottom lines, such as tax repatriation, than getting caught in politically charged fights over government surveillance.

Another industry lobbyist said Section 702 surveillance is “not a C-suite issue” that concerns chief executives in Silicon Valley like other issues, including encryption.

Companies have also been limited in how they can lobby for changes to the law because no comprehensive reform bill has been introduced yet in Congress, said Alex Abdo, a privacy advocate and staff attorney at the Knight First Amendment Institute at Columbia University.

A bipartisan group of lawmakers in the House Judiciary Committee is not expected to introduce such legislation until after Congress returns from its August recess.

The schism between tech companies and privacy groups was on display earlier this year in litigation in Ireland - Facebook argued customer data was sufficiently protected from U.S. spying programs, while an attorney for the American Civil Liberties Union testified that more protections were needed.

Snowden's leaks showed that Section 702 collects content of digital communications directly from the internet backbone and through a program formerly code named Prism where the NSA gathered data directly from several companies, including Facebook, Google, Apple and Microsoft Corp MSFT.O.

The statute also allows the FBI and others to query pools of data collection for U.S. information in what critics have derided as a “backdoor search loophole” that evades traditional warrant requirements.

The tech industry may become more engaged once the public debate becomes clearer, Abdo said. He added that a stronger position “would be enormously helpful to those that want to impose meaningful constraint on NSA surveillance.”

(This version of the story has been refiled to add dropped word “said” in paragraph 14)