The United States is helping a project to help clean-up Agent Orange contamination in part of Vietnam - the first such move since the war ended in 1975.
The work is taking place at the airport in the central city of Danang.
Millions of gallons of the toxic defoliant were sprayed over jungle areas during the war to destroy enemy cover.
Vietnam says several million people have been affected by Agent Orange, including 150,000 children born with severe birth defects.
The US government is providing $US41 million to the project, which is being carried out by two American companies in co-operation with the Vietnamese defence ministry.
The US has in the past helped fund some social services in Vietnam, but this is its first direct involvement in clean-up work.
An embassy statement said contaminated soil and sediment is to be excavated and then heated to a high temperature to destroy the dioxins.
USAID said the project would last until 2016.
The BBC reports there are dozens of other contamination sites where the defoliant was stored, including two more airports.
The United States and Vietnam resumed full diplomatic ties in 1995.