Americans are set to vote in one of the most divisive presidential elections in decades, pitting incumbent Republican Donald Trump against his Democratic challenger Joe Biden.
The first polls will open from 05:00 EDT (10:00 GMT) in Vermont.
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.
National polls give a firm lead to Mr Biden, but it is a closer race in the states that could decide the outcome.
In the US election, voters decide state-level contests rather than an overall single national one.
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.
Tuesday’s vote comes amid the ongoing coronavirus pandemic. The US has recorded more cases and more deaths than any other country worldwide, reporting more than 84,000 new infections on Monday alone.
As the nation counts down the hours to the vote, there are fears that pockets of post-election violence could break out. Businesses in the nation’s capital, Washington DC, and in New York City have been seen boarding up their premises due to concerns about unrest.
Where were Biden and Trump campaigning in the final hours?
On Monday, President Trump sprinted through four more battleground states.
In North Carolina, he told supporters that “next year will be the greatest economic year in the history of our country”.
The US economy saw record-breaking 33% growth in the third financial quarter of this year, following a record 31% contraction in the second amid the coronavirus crisis. Economists warn the damage inflicted the pandemic – the biggest decline in the US economy in more than 80 years – could still take years to overcome.
After North Carolina, Mr Trump headed to Scranton, Pennsylvania, the city where his opponent lived until he was 10. At a rally there he reminded his supporters that he won the state in 2016, despite polls suggesting he would lose.
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