Campaigning for Tuesday's presidential election in the US has entered its final three days.

President Barack Obama and his Republican challenger, Mitt Romney, have begun a round of visits to several swing states where the election is likely to be won or lost.

Opinion polls put the two candidates neck-and-neck, with Mr Obama holding a slight advantage in the battleground states.

Mitt Romney's first stop on Saturday was at a rally in New Hampshire, where he said he ''could not wait'' to get started.

''It's time to lead America to a better place,'' he added.