Democratic presidential hopeful Senator Barack Obama is to be backed by former rival John Edwards, his campaign says.
Mr Edwards, who was John Kerry's running-mate in the 2004 presidential race, has been one of the few senior Democrats yet to endorse a candidate.
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The endorsement comes a day after Mrs Clinton won the party's primary in West Virginia by a wide margin.
Mrs Clinton, like Mr Obama, had actively sought Mr Edwards's influential endorsement.
'Tricky case'
So far in the race for the Democratic presidential nomination, Mr Obama has won more of the delegates who will choose the party's nominee at the Democratic National Convention this summer.
He has also raised more money than Mrs Clinton.
The Clinton campaign has been hoping that she could pick up more endorsements than Mr Obama from the so-called "super-delegates", who get an automatic vote at the convention by virtue of holding a senior position in the party.
The BBC's Justin Webb says that with Mr Edwards's high-profile endorsement, Mrs Clinton's already difficult case has just become even trickier to make.
Mr Edwards was expected to make his endorsement alongside the Illinois senator at a rally in Michigan later on Wednesday.
(BBC)
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