Joe Biden took aim at Donald Trump at the White House Correspondents' Association dinner on Saturday night, saying: "Yes, age is an issue. I'm a grown man, running against a six-year-old”.
The President has faced repeated jibes from his likely rival for November’s election about his age of 80 - despite the Republican former president himself being 77.
"Age is the only thing we have in common... my vice president actually endorses me,” Mr Biden said at the annual black tie event which was hosted by comedian Colin Jost.
Mr Trump has not yet confirmed who will be his running mate in November to take on Mr Biden and the current vice president Kamala Harris.
Mr Trump reacted to the event by calling it "really bad" in a post on his Truth Social platform.
"Crooked Joe was an absolute disaster! Doesn’t get much worse than this!" he said.
Demonstrators holding banners outside the gathering at the Washington Hilton venue chanted about journalists' deaths in Gaza.
Hundreds of protesters encouraged journalists to boycott the annual event and shouted down administration officials as they entered.
A growing movement against the war in Gaza has dogged Mr Biden this year including at a $250-per-ticket March fundraiser at New York's Radio City Music Hall that was disrupted by protesters.
Mr Biden avoided the large protests at the front of the hotel by arriving through a back entrance, where he was greeted by smaller groups of protesters calling for a ceasefire.
The President also offered some advice to the press corps, saying: "I'm sincerely not asking you to take sides. I'm asking you to rise up to the seriousness of the moment.
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“Move past the horse race numbers and the gotcha moments and the distractions, the sideshows that have come to dominate and sensationalize our politics, and focus on what's actually at stake.”