WASHINGTON - US President Donald Trump claimed he had defeated Democratic challenger Joe Biden early on Wednesday morning (Nov 4), even though results from several battleground states that could swing the election had yet to be called.

Mr Trump said he would go to the Supreme Court to halt the counting of votes, accusing the Democrats - without evidence - of "fraud on the American public".

Meanwhile, Mr Biden told his supporters that he believed he was on track to win the election and urged that every vote be counted.

Neither candidate has the 270 electoral votes needed to win the election yet, in a very close race that will likely come down to the wire in the swing states of Pennsylvania, Wisconsin, Michigan, which were not expected to finish counting their votes until Wednesday or even Friday.

Vote counting often goes on for days after Election Day in the US, particularly so this year given the pandemic, which produced a surge of mail-in ballots that take longer to count.

"Frankly, we did win this election," said Mr Trump, speaking to supporters at the White House.

"Millions of people voted for us today," he said. "A very sad group of people is trying to disenfranchise that group of people, and we will not stand for it."

Mr Trump said that the results had been "phenomenal" and that he was winning Pennsylvania by "a tremendous amount".

He had been getting ready to go outside and celebrate, but it was suddenly called off, he added.

Claims rebuffed

But the President's premature declaration was dismissed by his ally and former New Jersey Governor Chris Christie, who told ABC News: "There's just no basis to make that argument tonight. There just isn't."

Facebook also swung into action to add labels to social media posts from the two presidential candidates as a reminder that vote counting is still underway.

"Once President Trump began making premature claims of victory, we started running notifications on Facebook and Instagram that votes are still being counted and a winner is not projected," said Facebook. "We're also automatically applying labels to both candidates' posts with this information."

"The President's statement tonight about trying to shut down the counting of duly cast ballots was outrageous, unprecedented, and incorrect," Biden campaign manager Jen O'Malley Dillon said in a statement as the election remained undecided.

"We have legal teams standing by ready to deploy to resist... and they will prevail," Dillon said

Biden urges 'patience'

The Democratic candidate earlier in the night had called for patience.

"We knew because of the unprecedented mail-in vote it's going to take awhile," he said. "It ain't over until every vote is counted, every ballot is counted."

"We knew this would go on, but who knew we would go into maybe tomorrow morning, maybe longer," Mr Biden said as he stood beside his wife, Jill, on an outdoor stage in his hometown of Wilmington, Delaware, half an hour past midnight.

Neck and neck

In a sign of how close the race has been, the only Electoral College vote to flip so far came from a congressional district in Nebraska that backed Mr Biden after favouring Mr Trump in 2016, Bloomberg reported.

Mr Trump won Florida, a crucial prize in the race to the White House that closed off former vice-president Biden's hopes for an early knockout in the election.

The President also won Texas, which Democrats had hoped might turn blue and entirely reshape the electoral map.

Mr Trump significantly outperformed in one of Florida's most populous counties, Miami-Dade.

After losing the county four years ago by 29 points, he lost by less than 8 to Mr Biden.

The county is diverse, with large Cuban and Venezuelan populations Mr Trump has courted by raising diplomatic and economic pressure on the socialist regimes in those countries.

He accused Mr Biden of sharing their politics.

Earlier, Mr Trump won Ohio and Mr Biden won Minnesota, states that each candidate had sought to take from the other but wound up politically unchanged from 2016.

Ohio was the first of several battleground states decided in the race.

Fox News and NBC News each called it for the incumbent just before midnight on Tuesday.

Mr Biden campaigned in the state the day before the election.

Mr Trump held multiple campaign rallies in Minnesota, a state he narrowly lost to Mrs Hillary Clinton in 2016.

But Mr Biden's strength in the urban parts of the state kept it in the Democratic column.

Mr Biden scored early wins in traditionally Democratic states, while Mr Trump won Republican strongholds, according to the Associated Press and networks.

More results

Other battleground states that remain undecided include North Carolina, Georgia, Pennsylvania, Wisconsin and Michigan.

Mr Trump holds leads in North Carolina and Georgia, though there are votes outstanding in each. Mr Trump won both states in 2016.

Mr Biden has won Arizona, a state Mr Trump won in 2016.

The results so far give Mr Biden a 238-213 lead in the Electoral College.

The first candidate to reach 270 will claim the presidency.

Mr Biden won Nebraska's second congressional district, Minnesota, Hawaii, California, Oregon, Washington, Colorado, New York, Virginia, Illinois, Maryland, New Jersey, Massachusetts, Connecticut, Vermont, Rhode Island, New Mexico, Delaware, District of Columbia and New Hampshire, according to the AP.

Mr Trump won Nebraska's other four Electoral College votes, Iowa, Idaho, Kansas, Arkansas, Indiana, Kentucky, Tennessee, South Carolina, Alabama, Mississippi, West Virginia, North Dakota, South Dakota, Wyoming, Louisiana, Oklahoma and Missouri, in addition to Ohio, Florida and Texas.

Nebraska is one of only two states, with Maine, that award an Electoral College vote to the winner of each congressional district.

Mr Trump won two districts and Mr Biden won one. Mr Trump won the state overall, giving him Nebraska's two remaining Electoral College votes.

Senate race

Even if they yet claim the White House, a "blue wave" that Democrats hoped would also give them control of both chambers of Congress may fall short.

Senate Majority Leader Mitch McConnell, a Kentucky Republican, was re-elected, the AP said.

Mr Lindsey Graham of South Carolina, the Senate Judiciary Committee chairman, was re-elected despite a Democratic challenger who badly out-raised him, and Senator Doug Jones, an Alabama Democrat, was defeated by Republican Tommy Tuberville.

Former Colorado governor John Hickenlooper, a Democrat, defeated Senator Cory Gardner, giving his party one pickup.

Other contested Senate seats remain undecided.

Black, Hispanic voters

Mr Biden is winning over Latino and African-American voters in numbers similar to Mrs Clinton four years ago, and is narrowing Mr Trump's margin among White voters, early exit polls from the AP show.

Mr Trump had a six-point lead among White voters in Tuesday's election.

Network exit polls four years ago showed him with a 20-point advantage among those voters.

Mr Biden led among Latino voters by a 2-to-1 ratio, and Black voters 13-to-1.

Mr Trump and Mr Biden had little more to do than wait as officials tally the votes, including millions of pivotal mail-in ballots that could take days to count.

Some Trump supporters posted on Twitter that they were headed to the White House for an election-night party, while the President's staff held a separate watch party in the West Wing.

A final outcome in the race may not be known until Wednesday or even later.

Elections officials in the key battlegrounds of Wisconsin, Michigan and Pennsylvania said they may be counting votes into the week.

Volatility persisted in US equity futures as investors worked to price in shifting odds for Mr Trump's re-election.

The odds of a second Trump presidency on the Betfair exchange pared some of their gains, and were trading at about 55 per cent.

Mr Trump and Mr Biden both projected confidence throughout Election Day, pointing to long lines at some polling stations as signs they were poised to win.

Violence feared

While there were reports of high voter turnout in states including Texas, Florida and Arizona, there were few signs of disturbances that many had feared.

In Charlotte, North Carolina, police arrested a man who was legally carrying an unconcealed firearm after he returned to a polling station authorities said he'd been banned from.

The New York Police Department said it will deploy thousands of officers on street patrol on Tuesday night to dissuade violence.

"Don't even try it," Chief of Department Terence Monahan said.

The wait continues

Mr Biden entered Election Day in a strong position, leading nationally by 7.2 percentage points as well as in most swing states, according to the RealClearPolitics polling average.

But the Election Day vote was expected to favour Mr Trump in large part because Democrats encouraged their supporters to cast early ballots.

Despite Mr Biden's advantage, some Democrats are spooked that Mr Trump could defy polls and win, just as he did in 2016.

But Mr Biden's lead over Mr Trump in national polls is greater than Mrs Clinton's was on Election Day in 2016.

RealClearPolitics had her ahead of Mr Trump nationally by 3.2 percentage points.

Mr Biden also has held consistent leads in some key swing states he needs to win, while in 2016 some of those states were infrequently polled and assumed to be a slam dunk for Democrats.

On Tuesday, Mr Trump predicted a "big red wave" among Republicans who cast their ballots in person rather than vote early or by mail as many Democrats had done.

"I think we're going to have a great night," Mr Trump told reporters when he stopped in at his campaign headquarters in Arlington, Virginia, before returning to the White House to await polling results and work the phones.

Voting takes place amid a deadly wave of the coronavirus pandemic, leading to millions of votes being cast by mail - a shift that could delay an official tally in some battleground states for days.

In Pennsylvania, for example, election officials could not begin processing early ballots until Tuesday, and it's unclear how long it will take officials to tally them.

Early turnout information suggested that Republicans had erased Democrats' lead in mail-in and early voting in Florida, a key state, Bloomberg reported.

Mr Michael Bloomberg, the founder and majority owner of Bloomberg LP, the owner of Bloomberg News, provided US$100 million (S$136 million) in support of Mr Biden and his running mate, Ms Kamala Harris, in Florida, half of that from his Independence USA PAC.

"If there's something to talk about tonight, I'll talk about it," Mr Biden said on Tuesday afternoon at a campaign stop in Wilmington, Delaware.

"If not, I'll wait till the votes are counted the next day."

The Biden campaign sees multiple paths to victory, while Mr Trump has a narrower route that includes recapturing Pennsylvania while protecting the other states he won in 2016.

A win for Mr Biden in those states would all but guarantee him a victory.

For live updates and results, follow our US election live coverage.