Joe Biden was edging closer to victory in the presidential race as he overtook the lead in the key battleground state of Georgia and gained ground in other tight contests.
With forecasts putting him just one state from victory, the Democratic challenger surpassed Donald Trump in Republican strongholds and was inching nearer to the lead in Pennsylvania.
Mr Trump, in order to stay in contention, has to take Georgia, a state not won by the Democrats since 1992 and where the president won by more than 200,000 in 2016.
Mr Biden appealed for calm and patience in stark contrast to the incumbent who used an extraordinary White House press conference to scatter unsubstantiated claims that he was being cheated out of re-election as he launched legal battles.
In Georgia, the former vice president took a slender lead over Mr Trump with an estimated 98% of the ballots counted.
But under state law if the margin between the pair is less than half a percentage point then a recount will be requested, which Mr Trump is all but certain to do.
The winner needs to collect 270 electoral college votes by winning states. Victory in his birth state of Pennsylvania would hand the presidency to Mr Biden by all counts with its 20 votes.
Georgia, with 16 electoral votes, is a more complicated scenario.
Not everyone agrees that Mr Biden has beyond all probability won in Arizona, and without that Georgia would leave him one vote short of overall victory.
He has secured victories in the battleground states of Wisconsin and Michigan, but Nevada and North Carolina also remain too close to call after Tuesday’s election.
Mr Trump on Thursday night alleged he is the victim of interference from “phoney polls” as well as “big media, big money and big tech” and the Republicans took court action in attempts to improve his chances of victory.
“If you count the legal votes, I easily won. If you count the illegal votes, they can try to steal the election from us,” Mr Trump said, with multiple major US television networks pulling away from his baseless claims, which he has provided no evidence to support.
Earlier Mr Biden had used a measured tone to say “democracy is sometimes messy, it sometimes requires a little patience”. He added that he had “no doubt” he will eventually be declared the winner.
“Each ballot must be counted and that’s what we’re going to see going through now and that’s how it should be,” he said from a stage in his hometown of Wilmington, Delaware, next to his running mate Kamala Harris.
Elections are run by individual state, county and local governments, and Mr Trump’s public comments have no impact on the tallying of votes across the country.
The Trump campaign requested a recount in Wisconsin and filed lawsuits in Pennsylvania, Michigan and Georgia.
But judges in Michigan and Georgia dismissed the actions launched by the Trump campaign. Additional legal action was also expected in Nevada, the campaign indicated.
Mr Biden’s campaign manager Jen O’Malley Dillon, said the president “knows he is losing” and had chosen to “push a flailing strategy, designed to prevent people’s votes from being counted”.
The Associated Press news agency, which PA relies on to call states, has projected Mr Biden as winning Arizona and its 11 electoral college votes.
That looks likely as he has a strong lead with 90% of the votes tallied, but Mr Trump’s campaign disagrees and other news organisations are not so certain.
The appearance of Mr Biden coming back from behind is an artificial one. Many of the outstanding ballots are postal votes and absentee ballots which are being added to the tally later than their in-person counterparts.