WASHINGTON - US President Joe Biden is "still experiencing an occasional cough", his doctor said on Wednesday.

The symptom is less frequent than a day earlier, White House physician Dr. Kevin O'Connor wrote in an update about Biden's recovery from a "rebound" COVID-19 case.

Fever-free, Biden "continues to feel well" and finished a light workout in the morning but his antigen testing remained positive, according to O'Connor.

Biden, 79, tweeted Wednesday noon that he had held a secure phone call with his national security team, alongside a picture of him wearing a mask and sitting behind a desk.

The White House said Biden is scheduled to deliver remarks virtually on abortion rights in the afternoon.

Biden tested positive for COVID-19 on July 21, and tested negative on July 26 after days of isolation and treatment. He tested positive again on July 30 in a "rebound" case, according to the White House.