In what could be the start of a new era of military and political co-operation, Vietnam said on Monday that it would give the United States permission to search for the remains of four soldiers who went missing during the Vietnam War.

Three previously closed sites will be open to excavation teams from the Joint Prisoners of War, Missing in Action Accounting Command, or JPAC. Two of the sites are the locations of fighter plane crashes, including the 1967 crash site of an F-4C Phantom in the central Quang Binh province and the crash of a Marine Corps F-4J in Quang Tri province, while the third was the scene of a ground battle in Kon Tum province near the borders with Laos and Cambodia in 1968.

We located the site in 2008 but soon thereafter the Vietnamese informed us that site was restricted for some reason, Ron Ward, a casualty resolution specialist at JPAC, told Reuters. So we're pleased to find out that today ... the restriction on that site has been lifted.

The new agreement was made during a meeting between Defense Secretary Leon Panetta and Vietnamese Defense Minister Phung Quang Thanh in Hanoi, and the two also exchanged artifacts from the war, including the diary of a Vietnamese soldier taken by U.S. marines in 1966.

Panetta is the most senior U.S. official to visit Vietnam since the end of the war in 1975, and the meeting is a follow-up of a defense co-operation memorandum signed last year. As part of its new armed forces strategy, the United States is looking to bolster military relations with Vietnam and other countries in the South Pacific.

During Panetta's visit, Prime Minister Nguyen Tan Dung also said that the United States should remove its ban on lethal weapons sales to Vietnam, Reuters reported.