Republican President Trump, 74, visited five battleground states while his 77-year-old Democratic challenger spoke at a campaign event in Pennsylvania, where the race also looks tight.

Mr Biden, a former vice-president, has a healthy national lead in the latest polls ahead of Tuesday's election.

But his advantage is narrower in key states which could decide the result.

More than 90 million people have already cast their ballots in early voting, putting the country on course for its highest turnout in a century.