US President Joe Biden tested positive for COVID-19 on Thursday and is experiencing "very mild symptoms," the White House said.

Biden, 79, will go on carrying out the duties of the office and has begun taking a course of the antiviral treatment Paxlovid, according to his press secretary, Karine Jean-Pierre.

"He is fully vaccinated and twice boosted and experiencing very mild symptoms," she said in a statement.

"Consistent with CDC guidelines, he will isolate at the White House and will continue to carry out all of his duties fully during that time," she said, referring to the Centers for Disease Control and Prevention.

Jean-Pierre said Biden had been speaking with his staff by phone and will continue to participate in meetings by phone and Zoom from the residence while he recovers. He will resume in-person work once he tests negative, she said.

The White House will provide a daily update on the president's health in the meantime, Jean-Pierre said.