Hillary Clinton throws her weight behind Obama at Denver convention

DENVER - Senator Hillary Clinton has thrown her weight behind Senator Barack Obama's quest for the US presidency, at the Democratic Party's convention in Denver.

In a widely-anticipated speech to delegates late Tuesday, she said it is time for Democrats to "unite as a single party with a single purpose".

Senator Clinton has been under enormous pressure to unite the Democratic Party behind Mr Obama's candidacy.

The woman who tried - but failed - in the primaries to win the party's nomination for the presidency was deeply emotional about having to address delegates after her recent defeat.

She thanked her supporters for standing by her throughout the bruising primary process that pitted her against Mr Obama. Bowing to the political needs of the moment, she urged them now to stand behind the man hoping to become America's first African-American president.

She said: "My friends, it is time to take back the country we love. And whether you voted for me, or you voted for Barack, the time is now to unite as a single party with a single purpose."

Her speech was a far cry from the attacks she unleashed on Mr Obama when they were both on the campaign trail. Then she argued he was too inexperienced, too green and too untested to be trusted with the presidency.

Underscoring what she used to say about Mr Obama, the McCain campaign is now even using one of her old advertisements in a new television advertisement launched from the Republicans' war room in Denver. The advertisement states : "Hillary was right. Vote John McCain".

But the Democratic Party's leadership believes that Americans will be inspired by the key message of this convention, that the country is craving the type of change that Mr Obama can deliver, and that the party is uniting around him.

Nancy Pelosi, speaker, US House of Representatives, said: "We've got to be thinking of what's going on in the homes of the American people and across America, because we don't have the luxury of leaving here not organised, focused, disciplined, unified, and inspired by this beautiful western convention that we have."

Delegates left the convention hall with Senator Clinton's speech echoing in their ears. Her own political future is now uncertain, but the Democrats hope she has helped to ensure Mr Obama's victory.

On Wednesday night, former president Bill Clinton will address the convention.