Americans are voting in one of the most divisive presidential polls in decades, pitting incumbent Republican Donald Trump against Democrat Joe Biden.
Polls have opened across the country after a long and bitter campaign amid the coronavirus pandemic.
More than 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.
Both candidates are using election day as an opportunity to drive home the messages they have been hammering to voters for the last few weeks.
The two rivals have radically different policies on several key issues. They have clashed bitterly during the campaign over how to handle the Covid-19 pandemic, and how to best handle the economy during this difficult period.
Mr Biden has accused Mr Trump of a haphazard response to the pandemic that he says has needlessly cost too many lives. But Mr Trump has downplayed the impact of Covid-19, saying the country is « rounding the corner ».
Mr Trump’s term has also been marked by racial tensions and contentious immigration policies.
Earlier on Tuesday, Mr Trump, sounding a little hoarse, spoke to Fox News by phone, saying he felt good about his chances of victory and predicting he would win « big » in key states such as Florida and Arizona.
« I think we have a really solid chance of winning, » he said. Asked when he would declare victory, he added: « When there’s victory. If there’s victory… there’s no reason to play games. »
Joe Biden visited his childhood home in Scranton in Pennsylvania – a key swing state – and addressed a crowd in the town, saying: « We’ve got to restore the backbone to this country. The middle class built this country – Wall Street didn’t. »
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