SAN FRANCISCO » Google is asking the Obama administration for permission to disclose more details about the U.S. government’s demands for email and other personal information transmitted online in an effort to distance itself from an Internet dragnet.

In a show of unity, Google rivals Microsoft Corp. and Facebook Inc. also supported the attempt to pressure the U.S. Justice Department to loosen the legal muzzle that limits disclosures about government surveillance authorized by courts to protect national security.

Google made its plea in letter Tuesday to Attorney General Eric Holder and FBI Director Robert Mueller. Google is trying to debunk media reports that the company has created a way for the National Security Agency to gain access to large amounts of its users’ online communications as part of a secret program code-named "PRISM."

The reports surfaced last week after a government contractor leaked confidential documents revealing the NSA has been tapping into the computers of Google Inc. and many other Internet services to retrieve information about foreigners living outside the U.S. The other companies linked to PRISM are: Microsoft, Facebook, Yahoo Inc., Apple Inc., AOL Inc., Paltalk, Google’s YouTube and Microsoft’s Skype.

All the companies and services have denied giving the U.S. government unfettered access to user data. The companies say they only turn over user data under legally binding orders, and try to regularly resist orders considered to be too broad.

Minimizing the appearance of their involvement in PRISM is important to the technology companies. The companies don’t want Web surfers to become paranoid about sharing personal information on their services or, worse yet, avoiding their websites altogether. Attracting big audiences helps the companies sell more advertising. Those ads command higher prices and run more frequently when the companies are able to decipher personal data and determine which parts of the audience are most likely to be interested in certain products.

The stakes are particularly high for Google, which sold $44 billion in digital advertising last year alone.

James Clapper, the director of national intelligence for the Obama administration, last week confirmed PRISM had been approved by a judge and is being conducted in accordance with U.S. law. He hasn’t listed the companies cooperating. Those identifications came from the PRISM documents leaked to The Washington Post and The Guardian, a British newspaper.

Even while acknowledging PRISM’s existence, Clapper has insisted the scope of its surveillance has been more limited than depicted in published reports.

Google also portrayed itself as an unwitting participant in the program. Executives at the Mountain View, Calif., company maintain that they didn’t know about PRISM until reading about it for the first time last week. Google insists it hasn’t been handing over user data on a broad scale, something the company believes it can prove if it receives clearance to disclose the number of requests that have been submitted under the Foreign Intelligence Surveillance Act, or FISA.

Federal law currently prohibits recipients of FISA requests from revealing information about them.

"Google’s numbers would clearly show that our compliance with these requests falls far short of the claims being made," David Drummond,Google’s chief legal officer, wrote to Holder and Mueller. "Google has nothing to hide."

In its own statement, Microsoft said it also wants to be more forthcoming if the Justice Department would allow it.

"Permitting greater transparency on the aggregate volume and scope of national security requests, including FISA orders, would help the community understand and debate these important issues," the Redmond, Wash. company said.

Ted Ullyot, Facebook’s general counsel, said the social networking leader wants to provide "a complete picture of the government requests we receive, and how we respond."