"I know that many Americans believe that this is not our fight," he said in a speech at Arlington National Cemetery, where America's war dead are buried. "But remember why many of the people are lying in these graves out here - because of what happened in Europe and because of what was allowed to go on too long before people intervened.
"What we are doing today will save lives, including American lives, in the future. And it will give our children a better, safer world to live in."
The President faces a tough job to maintain public support, with the war drifting into its third month and many Americans disturbed by the civilian casualties. In meetings this week he will also discuss what steps Nato might take if the air war fails to dislodge Serb troops from Kosovo. The US remains deeply sceptical of statements from Belgrade indicating that President Slobodan Milosevic will accept Nato's conditions for ending the war.
"The conflict in Kosovo can end in one of two ways," the White House said in a statement yesterday. "It could end tomorrow, if Milosevic agrees to the settlement and embraces peace. Specifically it means Milosevic must agree to the framework of the Rambouillet accords, which provides for Kosovar self-government and a Nato implementation force.
"If Milosevic doesn't choose this course, we will continue the Nato operation until his capacity to conduct operations against the Kosovars is seriously damaged."