Joe Biden has tripped and fallen at a graduation ceremony in a US Air Force academy.
The US president, 80, was quickly helped up by three people, and walked back to his seat unassisted. The incident happened in Colorado.
As the president was helped up, he pointed behind him, seeming to indicate what he tripped over.
White House communications director Ben LaBolt said Mr Biden was fine.
“There was a sandbag on stage while he was shaking hands,” he said.
Mr Biden, who stood for much of the hours-long ceremony to shake hands with graduates, appeared to trip over something and fell to his knees towards the end.
The president is running for re-election in 2024.
Doctors declared him healthy and fit for duty after a physical examination in February.
The US president was also seen stumbling on a flight of steps at the Itsukushima Shrine in Japan during his G7 visit last month.