A team of 12 U.S. military experts began a 15-to-20-day search with Vietnamese experts for evidence of the fates of Americans still missing from the Vietnam War, a U.S. embassy spokesman said Tuesday.

Spokesman James Williams said the American experts arrived in Vietnam Monday for searches expected to take them to three provinces in central Vietnam.He said the joint search was the 13th such effort since cooperation with Vietnam was stepped up in 1988 and the second since Vietnamese Deputy Prime Minister Nguyen Co Thach met U.S. officials in Washington in October.

"It is hoped the results achieved will reflect the increased cooperation pledged by the Vietnamese government during those talks," Williams said.

The U.S. experts, divided into two six-man teams, are from the Joint Casualty Resolution Center and the Army Central Identification Laboratory in Hawaii, he said.

He said the teams would work with their counterparts in the Vietnamese Office for Seeking Missing Persons and expected to spend about 15 to 20 days in the search.