A landmark scientific conference on the defoliant Agent Orange has ended in Vietnam with an agreement to continue studying the toxic lingering effects. United States and Vietnam continue to disagree on key issues.

More than 200 researchers from around the world came to the first joint conference on Agent Orange. Scientists from the United States and Vietnam hailed an unprecedented sharing of information, and resolved to work together in the future.

But the conference yielded little progress toward deciding how much responsibility the United States bears for spraying the toxic herbicide over Vietnam during the war more than 30 years ago.

Vietnam's vice minister of health accused the United States of waging chemical warfare decades ago, and asked for massive aid in repairing the damage. Pham Khoi Nguyen says Vietnam needs help treating children with birth defects and establishing health centers for other victims.

U.S. researchers say it is too early to talk aid money, and that more study is needed. William Farland of the Environmental Protection Agency cast fresh doubt on Vietnam's claim that one million people suffer dioxin-related illnesses in Vietnam.

During the Vietnam War, U.S. planes sprayed 18 million gallons of Agent Orange over what was then South Vietnam to kill trees and deny North Vietnamese guerrillas jungle cover. Agent Orange contains dioxin, which has been linked to cancer, birth defects and liver damage.

The United States pays disability and compensation to more than 8,000 of its own veterans exposed to Agent Orange. Congress ordered the payments in the face of a lawsuit. Vietnam argues that its civilian population is entitled to aid money too, and groups of victims here say they are preparing their own legal action.

U.S. researchers say it could take years to determine how much damage was done by Agent Orange, in part because Vietnam classifies nearly every birth defect in the country as a casualty.