DiCaprio helps launch clean-water campaign

Leonardo DiCaprio helped environmentalists launch an international campaign to draw attention to the billion people worldwide who don't have access to clean water.

"We are here to help raise awareness about what is one of the greatest challenges facing humanity today," said DiCaprio, speaking on World Water Day at the Clift Hotel in San Francisco on Tuesday with Global Green USA president Matt Petersen.

DiCaprio, who earned a best-actor nomination for playing Howard Hughes in "The Aviator," signed a petition that calls on President Bush and other government leaders to commit to a legally binding U.N. treaty declaring clean water as a basic human right.