BANGKOK, AUG. 13 -- Laos has agreed to renew efforts to resolve the problem of American servicemen still missing in action since the end of the war in Indochina, according to a joint statement released today by U.S. and Laotian negotiators in Vientiane.

The statement said the Laotian government "agreed to resume humanitarian cooperation with the United States" in looking for the remains of 549 Americans missing since communist forces defeated a U.S.-backed government in 1975 in Laos.

The statement also said "the U.S. government acknowledged the humanitarian problems of Laos and agreed to work within its capability to respond to them."

The two sides agreed to hold more talks soon, according to the statement. But neither American nor Laotian officials provided any other details on the outcome of the talks held Aug. 10 to 12.

The three-member U.S. delegation was led by National Security Council aide Richard Childress. The Laotian team was headed by Deputy Foreign Minister Souban Sarithirat.

Childress also participated in a U.S. mission that visited Vietnam for three days early this month to discuss ways to end the impasse between Hanoi and Washington on the MIA problem. Vietnam agreed during those talks to resume work on locating MIAs in exchange for a U.S. response to Vietnam's "humanitarian concerns."

Laos suspended cooperation on the MIA problem in February after a U.S. team was allowed to excavate a site in southern Laos where an AC130 Hercules gunship crashed in 1972 with 14 men aboard. The remains of eight servicemen were recovered in that excavation, bringing to 20 the number of remains repatriated from Laos since 1975.

Last year, the United States provided some funds to the U.N. High Commissioner for refugees to help repatriate Laotian refugees voluntarily returning from Thailand. More recently, the U.S. Congress introduced an amendment to the foreign aid bill authorizing President Reagan to spend $200,000 in humanitarian aid to Laos if it cooperated on the MIA issue.

Laotian officials indicated that they want the United States to help areas damaged during the war, while denying that they are trying to exchange remains for aid.

The U.S.-Laotian talks also dealt with narcotics production in Laos and the issue of Americans entering Laos illegally in search of MIAs.