Sanders vows to stay in Democratic nomination race

Bernie Sanders refused to concede defeat to Hillary Clinton on Tuesday, vowing to stay in the Democratic nomination battle despite his rival declaring herself the party's flagbearer for the US presidential race.

"We are going to fight hard to win the primary in Washington, DC," he told supporters in California, referring to the final nomination contest next Tuesday. 

"And then we take our fight for social, economic, racial and environmental justice to Philadelphia," where the Democratic convention will be held to formally nominate the party's candidate to challenge Republican Donald Trump for the White House.