The rally was the first time the former rivals shared a stage in public since Mr Obama clinched the Democratic nomination earlier this month and began trying to mend the rift caused by their epic 16-month campaign struggle.

This came after Mrs Clinton urged her top financial backers to support her former rival in the presidential race against Republican John McCain.

On Thursday night, Mr Obama met more than 200 of Mrs Clinton's biggest fund-raisers at a Washington hotel. Behind the scenes, the two sides were negotiating her future involvement with the campaign.

The former first lady told her donors they must make electing Mr Obama a priority, as she acknowledged that hard feelings remain on both sides after their hard-fought primary battle.

'But we are a family, and we have an opportunity now to really demonstrate clearly we do know what is at stake, and we will do whatever it takes to try to win back this White House,' she said.

Mr Obama announced that he would help pay off Mrs Clinton's more than US$20 million (S$27 million) campaign debt, personally writing a cheque for US$4,600 - the maximum allowed. His announcement that he will urge his donors to help pay Mrs Clinton's debts brought a standing ovation.

Some Clinton donors had been frustrated that the Democratic presidential nominee-in -waiting had not done more to help her pay the bills even as they are expected to help fund his campaign.

'I am going to need Hillary by my side campaigning during his election, and I am going to need all of you,' Mr Obama said, according to a report written by the only reporter allowed into the event and shared with other reporters afterwards.

The reporter recounted how Mr Obama had told his top fund-raisers this week 'to get out their chequebooks and start working to make sure Senator Clinton - the debt that is out there needs to be taken care of'. Her debt includes US$12 million of her own money. She has said she is not asking for help paying that back.

Three Clinton confidants are in talks with Mr Obama's campaign to work out details of her future involvement, including travel, her role at the national convention and resolution of her debt. Part of their argument has been that Mrs Clinton can spend more time helping Mr Obama if she is not raising money to pay her bills.

Mr Obama appears to be making headway with Clinton supporters. The latest Associated Press-Yahoo News poll, released on Thursday, found that 53 per cent of the Democrats who favoured her for the nomination two months ago now back Mr Obama for president.

ASSOCIATED PRESS, REUTERS