Donald Trump plans to send lawyers into key states as soon as voting ends, amid growing concern he'll try to claim victory before the votes are counted.
The US President has repeatedly refused to guarantee a peaceful transfer of power if he loses.
And he has called for the result to be announced "on the night" despite many states still counting postal votes that arrive after election day.
US Elections are never officially called "on the night" - in fact, it can often take weeks to certify the result. But TV news networks usually "project" a winner based on exit polls and other factors.
Reports published today suggested the President planned to claim victory if it appears he is "ahead" of Biden on election night.
But polls suggest more people who vote by mail are likely to vote for Biden - which could mean the projected result for key swing states could change after polling day.
This has been nicknamed the "red mirage" - in that it may appear that Republicans have won a state, but in reality they haven't.
And the President has claimed without evidence that votes received after polling day are vulnerable to fraud - particularly singling out the state of Pennsylvania.
Trump, it was reported, plans to claim he's won if he has a 'commanding lead' in Texas, Iowa, Georgia, Ohio, Florida, North Carolina and Arizona.
He dismissed the report as "false".
But he admitted he intends to send lawyers into key states to "dispute" ballots as soon as polls close.
We're going in the night of - as soon as the election is over - we're going in with our lawyers," he said ahead of a rally in North Carolina.
"If people wanted to get their ballots in, they should have gotten their ballots in long before that."
Some seven counties in Pennsylvania announced yesterday they were to wait until the day after the election to begin processing postal ballots.
This is likely to delay when US TV networks will be able to project a winner in the state - a key battleground in the election.
Trump won Pennsylvania by just over 44,000 votes in 2016 - less than 1% of the total.
