Washington, Jul 18 (IANS): US President Joe Biden has tested positive for Covid-19 as his bid for re-election faced fresh opposition from within his own Democratic party.

"Earlier today following his first event in Las Vegas, President Biden tested positive for Covid-19," Karine Jean Pierre, the White House Press Secretary said in a statement on Wednesday.

"He is vaccinated and boosted and he is experiencing mild symptoms," she added.

The campaign event in the crucial swing state of Nevada was cancelled and the President headed for his home state Delaware where he will self-isolate and recover.

Biden's re-election bid faced its severest challenge Wednesday when Adam Schiff, a senior Democratic member in the House of Representatives who is running for the US Senate, became the newest Democrat to call for the President to step aside. Schiff is very close to the former Speaker Nancy Pelosi, who together with other leaders of the party, is trying to steer the President towards the exit.

"Joe Biden has been one of the most consequential presidents in our nation's history, and his lifetime of service as a Senator, a Vice President, and now as President has made our country better," Schiff wrote in a statement. "But our nation is at a crossroads. 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," he added.

Biden has rejected all calls for him to step aside and has vowed to stay in the race, but his Covid-19 infection could seriously challenge his resolve given his age.

The White House doctor said in the same statement as released by Jean-Pierre, "The President presented this afternoon with upper respiratory symptoms, to include rhinorhea (runny nose) and non-productive cough, with general mailaise. He felt okay for his first event of the day, but given that he was not feeling better, point of care testing for COVID-19 was conducted, and the results were positive for the COVID-19 virus. Given this, the President will be self-isolating in accordance with CDC guidance for symptomatic individuals. PCR confirmation testing will be pending."

"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 per cent. The President has received his first dose of Paxlovid. He will be self-isolating at his home in Rehoboth," the doctor said.