US President Joe Biden has tested positive for COVID-19, the White House announced Wednesday.

Biden, who has been campaigning in Nevada, had to call off a keynote address at Unidos, a Latino civil rights organization's annual conference.

"He is vaccinated and boosted and experiencing mild symptoms," White House Press Secretary Karine Jean-Pierre said.

She added that he would continue his presidential duties from his home in Delaware. 

As he boarded Air Force One on his way home, he flashed a thumbs-up to reporters and said, "I feel good." He was not wearing a mask when he boarded but had one on during the flight. 

His doctor, Kevin O'Connor, said Biden was prescribed the antiviral drug Paxlovid and has taken his first dose.

Biden fighting for political survival

The setback came as more prominent Democrats call on Biden to drop out of the presidential race.

US broadcaster CNN reported that former House Speaker Nancy Pelosi had privately told Biden he could not win and staying in the race could harm Democrats' chances of recapturing the lower chamber of Congress.

US Democratic Representative Adam Schiff of California also publicly called on Biden to "pass the torch" and allow another Democrat to challenge Donald Trump in November.

Earlier, 81-year-old Biden said he would drop his reelection bid if doctors found he had a medical condition.

In an interview with BET journalist Ed Gordon, recorded before the COVID diagnosis, Biden was asked if there were any factors that would make him reevaluate his candidacy.

"If I had some medical condition that emerged, if somebody if the doctors came and said 'you've got this problem, that problem,'" Biden responded.

Biden has been fighting for political survival since a disastrous debate against Trump nearly three weeks ago. His tired and confused appearance during the debate sparked concerns about his age.

Biden under fire from within his own ranks

Nearly 20 Democratic members of Congress have called on Biden to withdraw from the presidential race in the wake of his debate performance.

Schiff became the latest, and the first after a would-be assassin took a shot at Republican presidential nominee former President Donald Trump.

"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," Schiff said.

ABC News reported that US Senate Democratic leader Chuck Schumer told Biden in a meeting on Saturday that it would be better for the country and the Democratic Party if he ended his reelection campaign. Schumer has not openly called for Biden to step down, but reports citing anonymous sources said the Senate leader had doubts about Biden's ability to beat Trump in November's presidential election. 

"I sat with President Biden this afternoon in Delaware; we had a good meeting," Schumer said in a statement released on Saturday.

In response to Schiff's remarks, the Biden campaign pointed to what it called "extensive support" for his reelection bid from members of Congress in key swing states as well as from the Congressional Black and Hispanic caucuses.

Schiff is considered to be close to former Democratic House Speaker Nancy Pelosi, who continues to wield significant influence in the party.

Pelosi recently said in an interview that it was up to Biden to decide whether he would run, making headlines by failing to back him explicitly. CNN reported on Wednesday that Pelosi told Biden that polling did not show him capable of beating Trump and that he could end up ruining the Democratic Party's chances at reclaiming a majority in the House of Representatives.

On Wednesday, powerful Schumer and House Democratic Leader Hakeem Jeffries encouraged the party to delay for a week plans to hold the virtual vote to renominate Biden.

The move to schedule the roll call, which would come weeks before the Democratic National Convention opens in Chicago in mid-August.

lo/sms (AP, AFP, dpa, Reuters)