US President Joe Biden has tested positive for Covid-19 while on a campaign trip to Las Vegas and is experiencing mild symptoms, according to the White House.
"I feel good," Mr Biden said, giving reporters the thumbs up as he leaned out of his limousine dubbed "The Beast," before boarding Air Force One to head for isolation at his home in Delaware.
The announcement came minutes after the head of a Latino union said Mr Biden had called to apologise that he could no longer address its members because he had been diagnosed.
It also comes as Mr Biden is under growing pressure to drop his reelection bid against Donald Trump after a disastrous debate performance sparked concerns about his age and health.
"Earlier today following his first event in Las Vegas, President Biden tested positive for Covid-19," spokeswoman Karine Jean-Pierre said in a statement.
"He is vaccinated and boosted and he is experiencing mild symptoms. He will be returning to Delaware where he will self-isolate and will continue to carry out all of his duties fully during that time."
Mr Biden's doctor was suffering from a runny nose and a "non-productive cough" along with "general malaise," the White House said in an accompanying note.
He was now receiving the Covid drug Paxlovid, it added.
"His symptoms remain mild, his respiratory rate is normal at 16, his temperature is normal at 97.8 and his pulse oximetry is normal at 97%," it added.
Janet Murguia, the president of the Unidos union, told the crowd about the diagnosis shortly before the White House announcement.
"I was just on the phone with President Biden, and he shared his deep disappointment at not being able to join us this afternoon," she said.
"The President has been at many events, as we all know, and he just tested positive for Covid.
"So of course, we understand that he needs to take the precautions that have been recommended."
Biden may drop election bid if 'medical condition' arises
Separately, Mr Biden has said that he might rethink his election bid if a "medical condition" emerged, according to an extract of an interview, as his health faces scrutiny after a disastrous debate.
"If I had some medical condition that emerged, if somebody, if the doctors came and said 'you've got this problem, that problem,'" Mr Biden told the media outlet BET in the sit-down interview taped earlier today, when asked what could make him rethink.
Mr Biden has faced fresh criticism as a heavyweight Democrat urged him to abandon his reelection bid and a backlash grew over plans for a virtual nomination before the party conference.
California Representative Adam Schiff urged Mr Biden to "pass the torch", becoming one of the highest profile Democrats to do so and the first since the assassination attempt against Donald Trump.
The 81-year-old has been fighting for political survival since the debate against Mr Trump nearly three weeks ago, in which his performance prompted concerns about his age.
"A second Trump presidency will undermine the very foundation of our democracy, and I have serious concerns about whether the president can defeat Donald Trump in November," Mr Schiff said in a statement to the Los Angeles Times.
Mr Schiff, who is expected to win a Senate seat this November, is a key White House ally in the legislature and came to nationwide prominence as lead prosecutor during then-president Mr Trump's first impeachment trial.
The chorus of Democrats calling for Mr Biden to step aside was briefly stopped by the attempt on Republican rival Mr Trump's life on Saturday, but has now started up again.
Around 20 House Democrats and one senator have now called on Mr Biden to leave the White House race but Mr Biden has refused, insisting he is best placed to beat Mr Trump.
Most polls show Mr Biden trailing in a tight race, with Mr Trump pulling ahead in key swing states but no dramatic movement since the debate debacle or shooting.
'Pretty damn good'
Mr Biden said his mental acuity was "pretty damn good" in an NBC interview yesterday, one of a series of unscripted outings in recent weeks aimed at showing he has what it takes.
He has blamed the debate on illness and jetlag, while his campaign says a series of recent verbal flubs are par for the course for a man famous for gaffes during a political career lasting more than four decades.
With pressure on Mr Biden mounting, Democrats said they plan to hold a virtual nomination for the president in the first week of August, ahead of the Democratic National Convention on 19 August.
Some Democrats have criticised the scheme, accusing the party of trying to fast-track Mr Biden's candidacy and avoid a full discussion of alternative choices.
Vice President Kamala Harris is considered the frontrunner if Mr Biden does drop out, although he has shown no sign he will.
Party chiefs say they need to carry out the virtual rollcall by 7 August, which is the deadline set by Republican-led state of Ohio for the submission of nominations.
Mr Biden otherwise risks not being on the ballot in Ohio, the home state of Mr Trump's new running mate JD Vance.
While Ohio's governor has signed a law giving Mr Biden more time, the DNC said it feared further legal challenges.
The DNC's rules committee said in a letter to politicians obtained by AFP that "no virtual voting will begin before 1 August," adding that it aimed to make a final decision next week.
"None of this will be rushed," it said.
"No matter what may be reported, our goal is not to fast-track," it added.
But several politicians are planning to sign a letter against the virtual nomination plan and others have criticised it, according to US media.
Mr Biden insists that Democratic voters support him, but a poll by the Associated Press and NORC Center for Public Affairs Research said that nearly two-thirds want him to step aside.
