The veterans claim that their pleas have been ignored while more than $180m has been paid to American and other soldiers who suffered from exposure to Agent Orange.

The Korean veterans, supported by the Seoul parliament, have filed a $1bn lawsuit in a Philadelphia federal court.

National Assembly deputy Seh-Jik Park told reporters in Washington that 30,000 of the 320,000 South Koreans who fought alongside US forces in Vietnam were harmed by Agent Orange.

'South Koreans excluded'

"All other Vietnam veterans from Australia, New Zealand and Canada have received compensation for their Agent Orange injury," Mr Park said. "Only in Korea, the veterans have been forgotten."

Agent Orange spraying harmed 'hundreds of thousands'

While the South Korean parliament supports the veterans' legal action, the Seoul government would prefer to settle the claim through diplomatic channels.

The US are South Korea's most important military ally and trading partner.

The US government has filed a motion to dismiss the veterans' suit. Washington claims it is a political matter and questions the jurisdiction of the Philadelphia court.

Millions of gallons

Vietnam blames child deformities on Agent Orange

US forces sprayed about 44 million gallons of Agent Orange over Vietnam between 1962 and 1971.

The aim was to kill crops and prevent North-Vietnamese troops from hiding in the thick undergrowth.

Experts believe that between 700,000 and several million people were exposed to the chemical causing cancer, miscarriage and birth defects.

In 1993, the manufacturers agreed to an out-of-court settlement with veterans' organisations. A $184m fund was set up to pay out compensations but the settlement did not include sufferers from South Korea.

Sensitive times

The veterans' legal action comes at a time of heightened sensitivity in South Korea after investigations into a recently reported mass killing by US soldiers of civilians at the beginning of the Korean War.

South Korea and the US launched inquiries in September after it was revealed that as many as 300 South Koreans may have been machine-gunned by Americans under the No Gun Ri railway bridge.

The killings are said to have taken place in July 1950.

American veterans have said they were told that North Koreans had been disguising themselves as South Korean refugees.