Former US Democratic presidential candidate John Edwards has endorsed Barack Obama's bid for the White House.

Speaking alongside Senator Obama at a rally in Grand Rapids, Michigan, Mr Edwards, who dropped out of the presidential race in January, said: "The Democratic voters in America have made their choice and so have I.

"There is one man who knows and understands that this is a time for bold leadership...there is one man who knows in his heart that it is time to create one America, not two - and that man is Barack Obama."

Political analysts believe his endorsement will severely damage Senator Hillary Clinton's chances of becoming the Democratic nomination.

But Senator Clinton's campaign team played down the importance of Mr Edwards' support for rival candidate Senator Obama.

"We respect John Edwards, but as the voters of West Virginia showed on Tuesday night, this thing is far from over," Clinton's campaign chairman, Terry McAuliffe, said in a statement.

Senator Obama currently leads the fight for delegates with 1,885 to Mrs Clinton's 1,118, according to AP estimates after Tuesday's West Virginia primary.

The successful candidate needs 2,025 delegates to secure the Democratic nomination.

Senator Obama has a lead of 14 (286 to 272) over Senator Clinton among the superdelegates who will cast the deciding votes in the Democratic race.

Five state primary contests remain - Oregon, Kentucky, Puerto Rico, Montana and South Dakota.

Senator Obama has also been endorsed by the National Abortion Rights Action League, one of the largest pro-choice groups in the US.