After a decades-long wait, families affected by the US use of toxic defoliant Agent Orange during the Vietnam War will benefit from a clean-up project financed by the US government - the first such move since the war ended in 1975.

The US says that the scheme will benefit anyone - from grandparents to infants - who has been affected by Agent Orange in the area near Danang Airbase in central Vietnam. The US sprayed millions of gallons of the defoliant over jungle areas to destroy enemy cover.

Danang was a key base in the US Agent Orange programme, and much of the 80 million litres (21 million gallons) of the defoliant used during "Operation Ranch Hand" was mixed, stored and loaded onto planes there.

Agent Orange was sprayed over vast swathes of jungle in South Vietnam in an attempt to flush out Viet Cong communist guerrillas by depriving them of tree cover and food. The contaminated soil and sediment is to be excavated and then heated to a high temperature to destroy the dioxins, a US embassy statement said.

A colourful ceremony to mark the launch of the project - involving women in traditional costume - could not mask the extent of the problem. Hanoi says up to three million people were exposed to Agent Orange, and that one million suffer grave health repercussions today, including at least 150,000 children born with birth defects.

Danang Airbase is one of three "dioxin hotspots" - alongside Bien Hoa and Phu Cat airbases - where concentrations of Agent Orange are nearly 400 times the globally accepted maximum standard. The area was sealed off only five years ago.

Vietnam and the US resumed full diplomatic ties in 1995 and have grown closer in recent years amid concerns over China's assertiveness over disputed territories in the South China Sea.

Speaking at the launch of the decontamination operation, US Ambassador David Shear described it as a "historic milestone". "We're cleaning up this mess," he said, adding the US would in future undertake an environmental assessment of another hotspot, the Bien Hoa airbase.