"I was wrong," Mr Christie, who is in a high-risk category for Covid-19 because of his weight and asthma, said in a statement.

"I was wrong to not wear a mask at the Amy Coney Barrett announcement and I was wrong not to wear a mask at my multiple debate prep sessions with the President and the rest of the team."

Mr Christie said he hoped his experience would encourage Americans to follow virus guidelines "in public no matter where you are and wear a mask to protect yourself and others".