Trump and Biden lock horns in US presidential race

Americans are voting in one of the most divisive presidential elections in decades, pitting incumbent republican Donald Trump against his democratic challenger Joe Biden.

Nearly 100 million people have already cast their ballots in early voting, putting the country on course for its highest turnout in a century.

Both rivals spent the final hours of the race rallying in key swing states.

To be elected president, a candidate must win at least 270 votes in what is called the Electoral College.

Each US state gets a certain number of votes partly based on its population and there are a total of 538 up for grabs.

This system explains why it is possible for a candidate to win the most votes nationally like Hillary Clinton did in 2016 but still lose the election.