WASHINGTON (Reuters) - A new Senate proposal to curb the government's bulk collection of Americans' telephone records and increase transparency about the program has White House backing and may get more traction with critics who have dismissed other bills as too weak.

Democratic U.S. Senator Patrick Leahy, chairman of the Senate Judiciary Committee, will introduce the legislation on Tuesday.

Because it does more to clamp down on the data collection exposed last year by former National Security Agency contractor Edward Snowden, Leahy's bill was expected to be more attractive to privacy advocates than a bill passed by the U.S. House of Representatives in May.

Many American technology companies have also been clamoring for changes after seeing their international business suffer as foreign governments worry they might collect data and hand it over to U.S. spy agencies.

The White House has been working closely with lawmakers, privacy experts and technology companies to secure Senate passage of what it considers critical legislation, National Security Council spokesman Ned Price said.

"Chairman Leahy has done remarkable work reflecting the equities of intelligence professionals while crafting privacy enhancements, and these efforts have yielded significant progress on issues vital to those stakeholders," Price said in an email on Monday.

President Barack Obama asked Congress in January to rein in the bulk collection and storage of records of millions of U.S. domestic telephone calls.

But the bill is not expected to come up for a vote in the Senate before Congress leaves for a five-week break on Aug. 1, which would prevent any action before next fall.

The House of Representatives passed the USA Freedom Act in May, but some privacy advocates and technology companies withdrew support because they wanted more extensive reforms.

Details of the Leahy bill have not been released.

But people who have seen recent drafts said it would go much further to reduce bulk collection of intelligence on Americans than the version that passed the House.

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Both the House and Senate measures would keep information out of National Security Agency computers, but the Senate bill would limit how much of the data the spy agency could seek.

So-called telephone "metadata" documents the numbers involved, when the calls were made, and how long they lasted. Metadata does not include the content of the calls.

The NSA had legal authority to collect and hold for five years metadata for all telephone calls inside the United States. Although several courts declared the NSA program illegal, Snowden's revelations caused a political uproar.

Under Leahy's proposal, analysts would have more limitations on the terms they use to search for information, with large geographical areas and service providers' names ruled out as "selectors," a privacy expert said.

The measure also would also create the position of privacy advocate who would represent the public before the court that oversees the data collection program.

(Reporting by Doina Chiacu, Roberta Rampton, Joseph Menn in San Francisco; Writing by Doina Chiacu. Editing by Andre Grenon)