His press secretary announced the news, adding that the president is “experiencing very mild symptoms”.
Press secretary Karine Jean-Pierre said Mr Biden, 79, tested positive this morning, adding that he is fully vaccinated and twice boosted.
The president said he’s “doing great” and tweeted: “Folks, I’m doing great. Thanks for your concern.
“Just called Senator Casey, Congressman Cartwright, and Mayor Cognetti (and my Scranton cousins!) to send my regrets for missing our event today. Keeping busy!”
Dr Ashish Jha, White House Coronavirus Response Co-ordinator, said the president’s mild symptoms began on Wednesday and include a runny nose, dry cough and fatigue.
He added that the president went to bed and felt fine, but did not sleep well.
The White House said he has begun taking anti-viral treatment, Paxlovid and will isolate while continuing to carry out duties “fully”
First Lady Jill Biden confirmed she has tested negative for the virus and had spoken to the president. She said “he’s feeling fine, just experiencing a few mild symptoms”.
The prime minister’s spokesman said Boris Johnson sends Mr Biden his “best wishes” and hopes he has a speedy recovery.
The president, who is the oldest person to serve as US president ever, was out just yesterday making a speech on climate change at a former coal plant in Massachusetts.
The White House added that Mr Biden has been in contact with members of staff by phone this morning and will participate in his planned meetings via phone and Zoom, resuming in-person work when he tests negative.
The statement continued: “The president’s last previous test for COVID was Tuesday, when he had a negative test result.”
Last month on 16 June, NBC News reported that the president tested negative for the virus twice during that week.
The disclosure came after Ms Jean-Pierre repeatedly refused to reveal the president’s testing status, a reversal from previous practice.
Read More: Joe Biden tests positive for COVID