Biden falls at US Air Force Academy graduation ceremony: 'I got sandbagged!'

President Joe Biden took a fall on stage at the U.S. Air Force Academy graduation ceremony in Colorado on Thursday.

Biden, who delivered the commencement address and proceeded to shake hands with graduates, fell near the podium as he stepped away and was quickly helped back to his feet by Secret Service agents and an Air Force officer.

The president, 80, walked away unassisted once he was upright. He continued to stand and greet people for the remainder of the ceremony.

He appeared to trip on a black sandbag being used to steady his teleprompter, according to pool reporters traveling with him, and pointed back at it after he got up.

"He's fine. There was a sandbag on stage while he was shaking hands," Ben LaBolt, the White House communications director, tweeted as videos of the incident circulated online.

Biden didn't take questions as he boarded Air Force One following the hourslong commencement.

White House press secretary Karine Jean-Pierre also said Biden is "totally fine" while she boarded Air Force One, according to the reporters traveling with Biden.

Later, returning to the White House, Biden said, "I got sandbagged!" as reporters shouted questions about how he was feeling.

He didn't add anything beyond that -- but did appear to try and show he was feel OK, doing a bit of footwork for the press before walking inside.

Biden's age and fitness have been a factor in his reelection campaign. He is the oldest sitting president in history and would be 86 at the end of second term should he win again in 2024.

A recent ABC News/Washington Post poll found that Americans said 62-33% that they thought Biden was not in good enough physical health to serve effectively.

Asked about his age after he announced he was running again, Biden said it will be up to voters to judge "whether or not I have it or don't have it."

"I respect them taking a hard look at it -- I'd take a hard look at it, as well. I took a hard look at it before I decided to run, and I feel good. I feel excited about the prospects," he told ABC's Chief White House Correspondent Mary Bruce in April.

Former President Donald Trump, who would also be in his 80s if elected, responded to being told about Biden's fall while campaigning in Iowa.

"I hope he's not hurt. The whole thing is crazy ... even if you have to tip-toe down the ramp," he said, poking fun at his own experience at the U.S. Military Academy at West Point in 2020 when his cautious descent down a ramp opened him up to similar criticism about his age.

"At the Air Force Academy? That's not inspiring," Trump added.

When speaking to graduates, Biden celebrated their work so far as he laid out the challenges that lie ahead.

"We have the finest military in the history of the world," he said. "And you've earned it. This day is the day to celebrate. And as your commander in chief, I'm honored to be here as you take on the duties of serving and defending our nation."

"In the years to come, you'll have even more asked of you," he continued. "You'll take on greater responsibilities, and you'll be challenged even beyond everything you've yet experienced."

ABC News' Libby Cathey and Gary Langer contributed to this report.