American President Joe Biden tripped and fell onstage while handing out diplomas at a graduation ceremony for the US Air Force Academy in Colorado on Thursday, media reports said.

Video footage of the incident has gone viral on social media.

After Biden shook the hands of more than 900 graduates, he turned to head back to his seat and started to motion as if he were going to jog. He then appeared to trip and fell down on the stage, reports NBC News.

Biden,80, is the oldest serving president of the country.

After he fell down onstage, he was helped back up to his feet.

The president had been standing for about an hour and a half to shake hands with each of the 921 graduating cadets, reports BBC.

Ben LaBolt, the White House communications director, said the President was 'fine'.

"He's fine. There was a sandbag on stage while he was shaking hands," he tweeted.