U.S. Secretary of State Hillary Clinton has met with leaders in Laos to discuss environmental protections for the Lower Mekong River Delta and issues dating back to the Vietnam War. She is the first secretary of state to visit Laos in 57 years.

The two sides talked about continued U.S. aid in helping dispose of unexploded cluster bombs dropped over Laos between 1964 and 1975. They also agreed to improve efforts to locate U.S. military personnel still missing from the war.

Clinton praised Laos for its efforts to reintegrate ethnic Hmong refugees who returned from Thailand in 2009.

She will travel to Cambodia later Wednesday to attend a regional conference.