Hillary Rodham Clinton will end her presidential campaign Saturday at an event in Washington. She will thank supporters and formally endorse rival Barack Obama, who clinched the nomination on Tuesday. The campaign said in a statement Friday that the event will take place at noon (1600 GMT) at the National Building Museum. The former first lady is expected to urge Democrats to unite behind Obama and help him defeat Republican John McCain in November. Clinton and Obama met privately at the home of California Sen. Dianne Feinstein Thursday night to discuss the campaign going forward.