President Joe Biden tweaked the concerns over his fitness for office and dug at his 2024 rival, former President Donald Trump, at the annual White House correspondents' dinner on Saturday night.

       Speaking at a ritzy Washington hotel to politicos and journalists alike, the 81-year-old commander in chief alluded to his past physical stumbles.

       "I told her, 'Don't worry, it's just like riding a bike,'" he said at one point, recounting a conversation with first lady Jill Biden about his Saturday speech. "She said, 'That's what I'm worried about.'"

       MORE: Trump and Biden say they are willing to debate

       Joe Biden also touched on age, set to be a defining issue of this year's presidential race -- but to knock the 77-year-old Trump rather than himself.

       "Of course, the 2024 election is in full swing and, yes, age is an issue. I'm a grown man running against a 6-year-old," Biden quipped. "Well, I feel great. I really feel great."

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       "Age is the only thing we have in common. My vice president actually endorses me," the president added, referencing former Vice President Mike Pence's refusal to endorse his former boss in the wake of Jan. 6.

       Biden also touched on Trump's legal troubles, including his recent appearances in court in New York City over hush money payments to adult film actress Stormy Daniels to cover up an alleged affair -- and, prosecutors claim, to hide the scandal from voters before the 2016 election. Trump denies all wrongdoing.

       "I had a great stretch since the State of the Union. But Donald has had a few tough days lately. You might call it 'stormy weather,'" Biden said.

       President Joe Biden laughs as host Colin Jost speaks at the White House Correspondents' As...Show more ---Show more

       Manuel Balce Ceneta/AP

       He used his speech, at times, to also sound a serious note, knocking Trump's criticism of the press as the "enemy of the people" and vowing to bring home Americans imprisoned abroad, calling out Paul Whelan and Wall Street Journal reporter Evan Gershkovich, both of whom are held in Russia on charges they and the U.S. deny.

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       The president concluded by issuing a call to the news media to focus on the "stakes" of the 2024 election, casting Trump as a threat to democracy -- a frequent attack that Trump has sought to reverse.

       MORE: Despite Trump's legal woes, polls show leading in swing states

       "Move past the horse race numbers and the gotcha moments and the distractions, the side shows that have come to dominate and sensationalize our politics and focus on what's actually at stake. …The stakes couldn't be higher," Biden said. "I have my role, but with all due respect, so do you."

       Trump, for his part, hit back on social media, lambasting the dinner -- which he skipped during his time in office, foregoing the customary speech the president also gives -- as "really bad" and Biden as an "absolute disaster."

       "Doesn’t get much worse than this!" he wrote.

       ABC News' Lalee Ibssa, Soo Rin Kim and Michelle Stoddart contributed to this report.