Decades after the U.S. gave Laos a horrific distinction as the world's most heavily bombed nation per person, Secretary of State Hillary Rodham Clinton pledged Wednesday to help get rid of millions of unexploded bombs that still pockmark the impoverished country — and still kill.

The U.S. dropped more than 2 million tons of bombs on the North Vietnamese ally during its "secret war" between 1964 and 1973 — about a ton of ordnance for each Laotian man, woman and child. That exceeded the amount per person dropped on Germany and Japan together in World War II.

Four decades later, American weapons are still claiming lives. When the war ended, about a third of some 270 million cluster bombs dropped on Laos had failed to detonate. More than 20,000 people have been killed in Laos since then by ordnance, according to its government, and agricultural development has been stymied.

Clinton, gauging whether a nation the U.S.