China has agreed to a long-standing U.S. request for access to sensitive military records that Pentagon officials believe might resolve the fate of thousands of U.S. servicemen missing from the Korean War and other Cold War-era conflicts, a Pentagon official said Monday.

The arrangement is scheduled to be publicly announced Friday in Shanghai after a final set of talks to work out certain details, according to Larry Greer, spokesman for the Pentagon's POW-MIA office.

The deal marks a modest step forward for U.S.-China military relations, which have been strained in recent years, in part by sharp U.S. criticism of China's military buildup. China has periodically cooperated with the Pentagon on matters related to the search for MIAs, but it has balked at repeated requests to open its military archives for documents of interest to the Pentagon.

Peter Rodman, a senior fellow at the Brookings Institution who dealt with the Chinese on the military archives issue when Donald H. Rumsfeld was defense secretary, said in an interview that the agreement is a positive step.

"It has special meaning to our military," Rodman said, because it could answer lingering questions about the fate of servicemen whose families have waited for decades to learn more. Rodman said the significance of the deal will depend on exactly what China has agreed to provide and how it is done.

China entered the Korean War on North Korea's side in the fall of 1950 and succeeded in driving U.S. forces out of the north. Chinese troops killed and captured thousands of American troops; the Chinese also managed many of the POW camps established in North Korea during the war.

More than 8,100 U.S. servicemen are still unaccounted for from the Korean War.

Greer said that at least initially, the arrangement to be announced on Friday will not give U.S. researchers direct access to Chinese records. Instead, Chinese archivists with security clearances acceptable to the People's Liberation Army will do the document searches and turn over relevant records to U.S. analysts.

"Our people, obviously, would prefer to have their own access," Rodman said.

Details such as the frequency and volume of the document searches, as well as expenses, are yet to be worked out, Greer said.

Charles A. Ray, the deputy assistant secretary of defense for POW-MIA affairs, was en route to Shanghai Monday to participate in the signing ceremony Friday, the spokesman said.

China has consistently maintained that all POW questions were settled at the end of the war, but nearly every U.S. administration since then has prodded Beijing to provide information on missing servicemen. The requests include cases of U.S. airmen who went missing after being shot down by the Chinese.

Declassified U.S. Army records from the 1950s make clear that the United States knew of hundreds of American prisoners in China during the Korean War, closely tracked their movements and feared for their lives.

In January 1998, then-Defense Secretary William Cohen asked top Chinese officials to open PLA record archives and other files. He got no explicit assurances at the time, but in follow-up contacts in the years since, the Chinese have said they would be willing to consider making some arrangement.

Greer said Ray is encouraged by progress that led to the agreement to be signed on Friday.

"This joint archival effort is expected to open more avenues of research to enable U.S. specialists to narrow their searches for the specific locations where American remains may be buried," Greer said.

After visiting China in March 2003 to press for access to military archives, Ray's predecessor, Jerry D. Jennings, declared, "Chinese records may well hold the key to helping us resolve many of the cases of American POWs and MIAs from the Vietnam War, the Korean War and the Cold War."

Former Defense Secretary Donald H. Rumsfeld also made a pitch for access during a visit in October 2005.

Many servicemen who are unaccounted for from the Korean War are believed to be buried at various sites in North Korea, and between 1996 and 2005 the Pentagon had some success in excavating such remains and indentifying them through forensic and DNA analysis. But in May 2005 the Pentagon suspended that cooperative effort, saying the North Koreans had created an unsafe environment for U.S. search teams.

A related issue is China's role in managing some of the war-time prison camps in North Korea where many U.S. soldiers died. And there have been questions about China having taken U.S. POWs from those camps to undeclared detention sites inside China.