Clinton has spent the past two months recovering from heart surgery.

With just over a week left till polling day, neither Kerry nor his rival George W Bush have a clear lead.

Clinton's appearance alongside Kerry will appeal to some undecided voters and African-Americans, says the BBC's Justin Webb in Washington DC.

The former president told ABC television on Sunday he was taking to the stage for the Kerry campaign - despite having been operated on less than two months ago - because "the differences between the two candidates and the courses they will pursue in the next four years are so profound."