Vietnam turned over to U.S. officials today the remains of five persons believed to be American servicemen missing in action during the Vietnam War.

The remains were handed over at Hanoi's Gia Lam Airport to a U.S. team headed by Col. Joe Harvey, the head of the Joint Casualty Resolution Center in Hawaii. The remains are to be flown to Hawaii for identification.

The return of the remains came amid signals here that Vietnam wants to improve ties with the United States and hopes that next month's 10th anniversary of the Communist victory over South Vietnam will mark a new chapter in relations with Washington.

However, an American request to participate in excavation of U.S. warplane crash sites in Vietnam has been turned down, according to Foreign Minister Nguyn Co Thach.

He said in an interview yesterday that U.S. National Security Council staffer Richard Childress and the widow of a missing American, Anne Griffiths, had requested such joint excavations during a visit here earlier this month. Laos recently permitted U.S. specialists to excavate a crash site near Pakse in southern Laos with a Laotian team, and some remains believed to belong to missing American airmen were found.

Thach said he told the Americans that "while we have no diplomatic relations, we cannot allow American teams to go into the countryside" to participate in joint excavations. However, he and other Vietnamese officials left open the possibility that Vietnamese teams would carry out new excavation.

"We will explore how to make more progress on this issue," Thach said.

He said Childress and Griffiths were taken to see the crash site of a B52 shot down in December 1972 during the "Christmas bombing" of North Vietnam. Thach said there are "perhaps still four remains" at the site about 25 miles from Hanoi.

While not specifically mentioning the normalization of relations with Washington as a condition for resolution of the missing in action (MIA issue, Thach hinted that diplomatic ties would bring progress in accounting for the nearly 2,500 American servicemen missing in the war. "If we can have normalization, the wounds of war will be healed," he said.

The United States has refused to open diplomatic relations with Vietnam because of the 1978 Vietnamese invasion of Cambodia and a U.S. desire to maintain good relations with China and noncommunist Southeast Asian countries.

In the interview, Thach said he had provided more details on the Vietnamese position on a political solution in Cambodia during talks here last week with Indonesian Foreign Minister Mochtar Kusumaatmadja. But he denied reports that he had given Mochtar five new proposals on the issue.