HANOI, Vietnam â€"  The Vietnamese government has announced it will open three previously restricted sites for excavation by the U.S. to search for troop remains from the war.

The announcement from Vietnam Minister of Defense Phung Quang Thanh comes as U.S. Secretary of Defense Leon Panetta and his Vietnamese counterpart participated in a first-of-its-kind joint exchange of artifacts from the war in Hanoi.

A Department of Defense spokesman said in a statement the department believes Joint Prisoners of War, Missing in Action Accounting Command (JPAC) research teams will greatly benefit from access to the new sites in their search for the approximately 1,200 U.S. service members still missing in Vietnam.

"The Department of Defense believes these sites are critical to locating missing-in-action troops from the Vietnam War," spokesman George Little said.

In the artifact exchange, Panetta gave his Vietnamese counterpart the Vũ Ðình Ðoàn diary, which was taken by Robert Frazure, United States Marine Corps following Operation Indiana in 1966. 

In turn, Quang Thanh presented personal letters of U.S. Army Sergeant Steve Flaherty, who was killed in action in 1969.

Both leaders agreed to return the artifacts to the relatives of the soldiers. 

The bilateral meeting in Hanoi came a day after Panetta visited the deepwater port and former American military base at Cam Ranh Bay in Vietnam as part of an effort to promote a closer military partnership with the Vietnamese and reassert the U.S. presence in Asia.

The trip was an important sign of American aspirations in the region. Panetta indicated that the U.S. Navy would like to once more have regular access to the bay, which commands a strategic location on the South China Sea, The Wall Street Journal reported.

On Saturday, before arriving in Vietnam, Panetta announced that by the next decade, 60 percent of U.S. Navy warships would be stationed in the Pacific.

Panetta is in Asia as part of an effort to explain the new American strategy in the Pacific region and begin to put it into effect by trying to make progress in developing deeper partnerships with Vietnam, Singapore and India.

Fox News' Jennifer Griffin, Newscore and The Associated Press contributed to this report.