The bombs, as one Laotian recalled, "fell like rain", US President Barack Obama said on a visit to Laos, a first for any sitting US president."Given our history here, I believe that the United States has a moral obligation to help Laos heal," he said.He referred to America's secret and devastating bombing of Laos during the Vietnam War in the 1960s and 70s.Some $90m (£68m) will be spent over three years for the removal of cluster bombs and other unexploded ordnance.That compares to $100m spent in the last 20 years.Mr Obama did not offer an apology for the bombing.