Joe Biden is closing in on Donald Trump in the key battleground of Georgia, hoping to flip a third state from the Republicans and put himself within touching distancing of the White House.

The Democrat challenger is now 31,000 votes behind - a much smaller gap than the 372,000 he trailed behind by 24 hours ago - as counting continues in a series of knife-edge elections.

But his fortunes have begun slipping away in Arizona - one of his highly-prized targets in the southern Sun Belt.

There, the race has tightened to give Mr Biden a lead of just 79,000.

Only a handful of "toss up" states are left in play as he and Donald Trump vie for the crucial 270 Electoral College votes needed to win the US presidency.

So far, Mr Biden is the closest on 253 - also leading in the popular vote and breaking the record for the most number of votes ever cast for a presidential candidate.

Mr Trump has 214 Electoral College votes, also surpassing the number of total people who backed him in 2016 by more than three million.

Despite election administrators appeals for patience and calm, the stakes have been significantly raised by Mr Trump's campaign launching legal challenges.

"Poll watchers" have amassed outside some counts, with the mood febrile as they chant and demand access to the counting halls, while protests against Mr Trump raged in New York and Pennsylvania.

And the president himself has threatened to take his fight to the Supreme Court, with his lawyer Rudy Giuliani wildly speculating, without evidence, that Mr Biden may have voted illegally 5,000 times.

Mr Trump himself has already claimed victory in the election overall and in states where no result has been announced - Pennsylvania, Georgia and North Carolina.

But speaking from Delaware, where he hoped to be able to make a victory speech on election night, Mr Biden on Wednesday told supporters it is "clear" he is on course to win.

"I'm not here to declare that I've won," he said, but pointed out that in undeclared races, he is leading by more votes than Mr Trump won them by at the last election.

He added: "We the people will not be silenced; we the people will not be bullied; we the people will not surrender."

Despite his confidence, Mr Biden will likely be disappointed he did not take an earlier, convincing lead once the results began trickling in.

He failed to capture swing states such as Florida and Ohio that would have already cemented his position, and fell short of taking "ruby red" Texas under the landslide some pollsters had forecasted.

But Mr Biden did gain momentum with his first major successes on Wednesday, taking Wisconsin and Michigan, according to a Sky News/ NBC forecast.

In a bid to thwart that, Mr Trump accused his opponents of a "major fraud" and launched two lawsuits, also demanding a recount in Wisconsin.

"How come every time they count Mail-In ballot dumps they are so devastating in their percentage and power of destruction?" he wrote, as part of a series of tweets trying to cast doubt over the election process.

Twitter then stepped in to censor several his messages, warning readers: "Some or all of the content shared in this Tweet is disputed and might be misleading about an election or other civic process."