President Donald Trump erupted Thursday in a tirade of unsubstantiated claims that he has been cheated out of winning the US election as vote counting across battleground states showed Democrat Joe Biden steadily closing in on victory.

"They are trying to steal the election," an increasingly isolated Trump said in an extraordinary statement at the White House two days after polls closed.

Providing no evidence and taking no questions afterward from reporters, Trump spent nearly 17 minutes making the kind of incendiary statements about the country's democratic process that have never been heard before from a US president.

According to Trump, Democrats were using "illegal votes" to "steal the election from us."

"If you count the legal votes, I easily win," he claimed. "They're trying to rig an election. And we can't let that happen."

Beyond the rhetoric, Trump's complaints were specifically targeting the integrity of the huge number of ballots mailed in, rather than cast in person on Election Day.

The big shift to postal ballots this year reflected the desire of voters to avoid risking exposure to Covid-19 in crowded polling stations during a pandemic that has already killed close to 235,000 Americans.

However, because Trump often denied the seriousness of the virus and told his supporters not to support mail-in ballots, far fewer Republicans took advantage of the option, compared with Democrats.

- Biden closes in -

Several major US television networks cut away from live coverage of Trump's event and there were signs of cracks in Republican support.

Representative Will Hurd called Trump's call to stop vote-counting "dangerous and wrong," saying it "undermines the very foundation this nation was built upon."

And conservative Rupert Murdoch's powerful media empire appeared to shift tone, with his New York Post calling Trump's fraud allegations "baseless" and Fox News refusing Republican pressure to rescind its projection that Trump would lose Arizona, vital for his chances.

Trump's rant came as returns from still undeclared states around the country showed Biden trending toward victory.

Biden, 77, was just one or at most two battleground states away from securing the majority to take the White House. Trump, 74, needed an increasingly unlikely combination of wins in multiple states to stay in power.

Biden, who has promised to heal a country bruised by Trump's extraordinarily polarizing four years in power, appealed for "people to stay calm."

"We have no doubt that when the count is finished, Senator (Kamala) Harris and I will be declared the winners," he said in comments to reporters in his hometown of Wilmington.

"The process is working," he said. "The count is being completed. And we will know soon."

- All about Pennsylvania? -

In Georgia, a generally Republican state, Trump had a razor-thin and fast vanishing lead of fewer than 1,900 votes.

In Arizona and Nevada, Biden held on to slim leads. If Biden wins both those states he would also win the presidency.

But the biggest piece of the puzzle was Pennsylvania, where Trump's early lead was again steadily draining away, as election officials homed in on processing mail-in ballots, which are more typically cast by Biden supporters.

The Democratic hopeful currently has 253 of the 538 electoral college votes divvied up between the country's 50 states. He has 264 with the inclusion of Arizona, which Fox News and the Associated Press have called in his favor, but other major organizations have not.

If Biden took Pennsylvania, he would grab 20 more electoral college votes, thereby instantly topping the necessary 270 for overall victory.

Latest results showed Trump's lead in the state had shrunk to around 42,000 votes, with most votes yet to be counted coming from Democratic stronghold Philadelphia.

- Protests across country -

Trump's campaign continued to insist that the president has a way to win, citing pockets of Republican support yet to be counted.

But Trump's overwhelming focus was on claiming, without evidence, that he was a victim of mass fraud.

Trump prematurely declared victory Wednesday and threatened to seek Supreme Court intervention to stop vote-counting but it has continued nonetheless.

Since then, his team fanned out across the battleground states challenging the results in court and his supporters converged outside election offices in several cities.

In Las Vegas, Trump backers wearing red "Make America Great Again" hats demanded to see ballots being processed.

Brando Madrigal said he wanted to verify that the votes are "not coming from the people who died with Covid, people who are out of state, people who don't have the ability to vote because they don't have the papers."

But while Trump was demanding that counting be halted in Georgia and Pennsylvania -- where he is leading -- his supporters and campaign insisted that it continue in Arizona and Nevada, where he is trailing.

Bob Bauer, a lawyer for the Biden campaign, dismissed the slew of lawsuits as "meritless."

"All of this is intended to create a large cloud," Bauer said. "But it's not a very thick cloud. We see through it. So do the courts and so do election officials."

US networks break from live Trump address

Several US TV networks late Thursday halted live coverage of Donald Trump's first public appearance since election night after concluding that the president was spreading disinformation.

Trump unleashed a flood of incendiary and unsubstantiated claims in a 17-minute address, insisting that Democrats were using "illegal votes" to "steal the election from us."

The president spoke as late vote counting in battleground states showed Democrat Joe Biden steadily closing in on victory. 

"OK, here we are again in the unusual position of not only interrupting the president of the United States but correcting the president of the United States," said MSNBC anchor Brian Williams, as the network quickly ended its live coverage.

NBC and ABC News also pulled the plug on their live coverage of Trump. "What a sad night for the United States of America to hear their president say that, to falsely accuse people of trying to steal the election," said CNN's Jake Tapper. 

He described it as "lie after lie after lie about the election being stolen," with no evidence, "just smears."

Hanging on results of key states

The outcome of the US presidential election remained in the balance late Thursday as a handful of battleground states complete their vote counts.

Democrat Joe Biden has racked up at least 253 of the 270 electoral votes that he needs, according to US network projections -- and 264 if Arizona is included, which Fox News and The Associated Press have called in his favor.

Donald Trump has amassed 214 electoral votes so far, and is still in contention in several states that would afford the Republican incumbent a path to reelection.

Expected to report final vote counts Thursday night or Friday are Georgia (16 electoral votes), North Carolina (15), and Nevada (6).

However, mail-in ballots sent on or before Election Day in North Carolina can be counted until November 12.

Biden could reach the magic number to gain the White House with a win in any of the three, if he keeps Arizona. Trump needs to capture all three to stay competitive.

Here is a look at the situation in the key states that are still up for grabs, and paths to victory for each candidate:

- Nevada -

Nevada, where Biden is favored, could put him precisely at the number needed to win, if he keeps Arizona. With more than 89 percent of the vote counted, Biden was leading by less than 11,500 votes.

- North Carolina -

In North Carolina, Trump had a comfortable lead of around 77,000 votes with 95 percent of the ballots, about 5.38 million, tabulated.

- Georgia -

In Georgia, Trump's razor thin lead over Biden has been steadily slipping away to less than 2,500 votes, with about 98 percent counted.

Biden could pull in the lion's share of the final votes being counted -- less than 19,000 remained as of Thursday evening -- which include thousands in Democratic-leaning areas.

Georgia has not chosen a Democrat for president since Bill Clinton in 1992.

- Pennsylvania -

Pennsylvania is the biggest prize remaining, with 20 electoral votes. As in Georgia, Trump is currently leading, but the majority of votes left to be counted are in Democratic-leaning areas like greater Philadelphia.

As of Thursday evening, Trump's lead had dwindled to about 50,000 votes, with 92 percent of the ballots counted.

- Arizona -

One wild card that could upset these calculations: Arizona. Fox News and The Associated Press have already called the state's race in Biden's favor, but other networks including CNN and NBC have said it's still too close to call.

Arizona's Secretary of State Katie Hobbs told ABC News that she did not expect a final count on Thursday -- but also that she doesn't expect a recount.

"It's not looking like today, probably closer to tomorrow that we'll be closer to getting through all those ballots," Hobbs said.

On Thursday evening, Biden had a lead of about 46,000 votes with about 90 percent of the ballots counted.

- Paths to victory -

Much of the delay has resulted from a flood of mail-in ballots due to the coronavirus pandemic -- and those votes have tended to favor Democrats.

If Biden's lead in Arizona holds, and he wins Nevada or Georgia, he would pass the threshold of 270 electoral votes.

Should Trump hold North Carolina and Georgia but lose Arizona, he must take Nevada as well as Pennsylvania to win.

Simply winning Pennsylvania -- where Trump leads but faces a possible onslaught of pro-Biden mailed ballots -- will not be enough for the president, even if he takes Alaska's three electoral votes as expected.

Much to Trump's chagrin, Pennsylvania has decided to allow mailed ballots sent by Election Day but received up to three days afterwards to be counted. Authorities expect to complete the count by Friday.

Another factor that could keep the battle alive: the Trump campaign has unleashed a legal blitz in key states vital to the incumbent's re-election.

It has sued to disqualify late-arriving ballots in Pennsylvania, sued in Nevada and Georgia over alleged irregularities, and has demanded a recount in Wisconsin.