CAM RANH BAY, Vietnam â€"  U.S. Defense Secretary Leon Panetta has arrived at a former U.S. air and naval base at Cam Ranh Bay, Vietnam, becoming the most senior American official to go there since the war ended.

Panetta says he hopes to encourage efforts with Vietnam to locate and identify more of the U.S. war dead who are still missing.

He plans to visit the USNS Richard E. Byrd, a cargo ship operated by the Navy's Military Sealift Command. The ship has a largely civilian crew and is used to move military supplies to U.S. forces around the world.

The U.S. military's Joint POW/MIA Accounting Command has six recovery teams and two investigative teams in Vietnam searching for troop remains. There are about 1,200 unaccounted for service members believed to be in Vietnam.