Congressional negotiators agreed this week to undo part of a Watergate-era law that prevented former president Richard M. Nixon from taking his tapes and papers with him, but they said the records would still have to be processed here before being released to establish the presidential library that Nixon and his family always wanted.

The change, sponsored by Rep. Thomas M. Davis III (R-Va.), was tucked into an appropriations bill without public hearing and approved last night by a House-Senate conference committee. Democrats who agreed to it were mollified by the promise of continuing public access under safeguards Congress formulated in 1974.

Officials at the Nixon Presidential Materials project in College Park said it would take eight to 10 years before they can finish the work of making the records public.

Davis led the drive for repeal in response to the urgings of Nixon’s daughter Julie Nixon Eisenhower, a longtime friend who recently visited Davis and other lawmakers. He is chairman of the Government Reform Committee, which has jurisdiction over the National Archives and its presidential library system. Half a dozen of Washington’s most expensive lobbyists, hired in August by the Nixon foundation, also worked both sides of the aisle.

Julie Eisenhower and her husband, David, are “two of my best friends on the planet,” Davis said yesterday. “They were doing fundraisers for me when I was running for [Fairfax] county supervisor 25 years ago.”

As finally crafted, he said, the bill “was not controversial. Public access is not going to be affected.”

Under the 1974 law, enacted to keep Nixon from destroying his tapes and other records, all the material was to be kept by the archivist of the United States in Washington “or its metropolitan area,” except as needed for legal proceedings. The bill approved this week would eliminate that provision and give Archivist John W. Carlin the authority to transfer the materials to a presidential library built with privately raised funds but staffed by the National Archives.

The bill notes, however, that nothing in the new measure “may be construed as affecting public access” under 1974 rules. It emphasizes making public “the full truth, at the earliest reasonable date, of abuses of governmental power popularly identified under the generic term ‘Watergate.’ “

Lawmakers also stressed the need to make public records “of general historic significance” but said Nixon and his heirs should have “sole custody” of personal and private material.

The Nixon project’s director, Karl Weissenbach, said that his staff has more than 37 million pages of documents to process, out of a total of 46 million, because of a primary focus on the tapes, and because of litigation brought by the Nixon camp. Tapes chronicling abuses of power have been made public, but many others remain to be reviewed.

In addition, Weissenbach said, it will take three to five more years to finish cutting up the original White House tapes in response to the Nixon estate’s demand that personal material on the recordings -- often less than a minute each but adding up to 819 hours -- be destroyed. The splicing, which has to be done with a single-edged razor blade, began in 1998.

Aides to Rep. Henry A. Waxman (Calif.), the ranking Democrat on Davis’s committee, said talks with Davis and his staff were “a constructive process” and that Nixon foundation lobbyists from Cassidy & Associates were helpful.

“Up here these days, Republicans usually don’t ask when they want to make changes,” said Waxman’s chief of staff, Philip M. Schiliro. “What was different here was Tom Davis came in and said, ‘What are your concerns, we want to address them.’ “

John Taylor, director of the privately operated Nixon library and birthplace in Yorba Linda, Calif., said he is looking forward to negotiations with the National Archives over a presidential library there that could shine a spotlight on all of Nixon’s records. He called Davis’s bill, added to the appropriations measure by Rep. Ernest J. Istook Jr. (R-Okla.), “a first step in abolishing the anomaly” of Nixon being the only president between Herbert Hoover and Bill Clinton without a government-operated library.