More than 100 million US citizens cast their ballots in advance of Tuesday's election, according to the US Elections Project watchdog, a record figure largely attributed to the Covid-19 pandemic.
The ballots, which were mailed in, deposited in drop boxes or cast at polling stations ahead of Tuesday, represent more than 72 percent of the total number of ballots cast in the 2016 presidential election, according to the tally by the watchdog based at the University of Florida.
In the states of Texas, Hawaii, Washington and Montana the number of early votes exceeded the total number cast there in 2016.
Four years ago, some 57 million voters had cast an early ballot, according to the US Election Assistance Commission.
Of the more than 100.2 million early votes cast this time around, more than 64.5 million are mail-in ballots – an option widely expanded across the country in response to fears of Covid-19 contagion in crowded polling stations.
Several key states – including Michigan, Pennsylvania and Wisconsin – do not begin counting mail-in ballots until Election Day itself, fuelling fears a final result could take days.
US President Donald Trump, a Republican, has launched repeat assaults on the credibility of mail-in voting, often claiming without evidence that the process will be rigged against him.
Trump's Democratic opponent, Joe Biden, leads the race in national polls and in many of the battleground states that will decide the high-stakes race.
Trump: US 'entitled' to know result on same day
Speaking on Tuesday, Trump again sought to sow doubt, saying the country was "entitled" to know who won on the day of the vote.
"You have to have a date, and the date happens to be November 3," he said during a visit to Republican National Committee offices in Arlington, Virginia.
"And we should be entitled to know who won on November 3."
Trump was referring mainly to his disagreement with a US Supreme Court refusal to intervene in a decision allowing Pennsylvania to continue to count mailed ballots received up to three days after the election.
The move was made due to logistic complications as the country copes with the coronavirus pandemic, which has led to a flood of mailed ballots.
Pennsylvania is seen as an important swing state in the election, and both Trump and Biden have repeatedly campaigned there in recent days.
"You can't have these things delayed for many days and maybe weeks," Trump said as Americans voted nationwide and with more than 100 million people having cast early ballots.
"You can't do that. The whole world is waiting. This country is waiting. But the whole world is waiting."
Asked whether he had written an acceptance or concession speech, Trump said he had not.
"You know, winning is easy," he said.
"Losing is never easy – not for me it's not."