WATCH: Bare-faced Biden breaks White House mask rules, asks attendees not to rat him out

Upon taking the stage, he half-jokingly asked attendees not to rat him out for failing to wear the face covering, pointing out that he'd tested negative for the virus.

"Let me explain to the press," Biden said as he entered the room. "I've been tested again today. I'm clear across the board."

"They keep telling me ... I've got to keep wearing it," he added, holding up the black mask, "but don't tell them I didn't have it on when I just walked in."

His comments drew laughter from those in the crowd.

Following Jill Biden's diagnosis, White House Press Secretary Karine Jean-Pierre announced that would have to wear a mask indoors while he was around other people.

"Since the president was with the First Lady yesterday," she said, "he will be masking while indoors and around people, in allignment with CDC guidance, and as has been the practice in the past, the president will remove his mask when sufficiently distant from others indoors and while outside as well."

Jean-Pierre added that Biden was adhering to the CDC recommendations for those who come in contact with someone who tests positive, which include a combination of masking, testing, and monitoring for symptoms.

The press secretary went on to note that as the summer months give way to fall and winter, people will have access to more tools to prevent and treat Covid, including updated vaccines and at-home tests. She encouraged vulnerable Americans to get innoculated against not only Covid, but influenza and RSV as well.