Trump, 72, says: 'I'm so young I can't believe it. I'm the youngest person'

Billionaire is oldest man to ever assume US presidency

Donald Trump, in a jab at 76-year-old Democratic rival Joe Biden, boasted he is the "youngest person" during a conversation with reporters outside the White House.

The US president, 72, was asked by one journalist “how old was too old to president”, in light of Mr Biden’s announcement he will run for the Democratic presidential nomination.

“Well I think that, I just feel like a young man, I’m so young! I can’t believe it, I’m the youngest person,” Mr Trump, who is the oldest man to ever assume the presidency, shouted over the roar of Marine One.

“I am a young, vibrant man. I look at Joe, I don’t know about him, I don’t know. I would never say anyone’s too old, but I know they’re all making me look very young, both in terms of age and I think in terms of energy. I think you people know that better than anybody.”

Despite Mr Trump's claim, of the major Democratic contenders only Mr Biden and Bernie Sanders are older than the president. Pete Buttigieg, who Mr Trump said he was "rooting for" on Thursday, it the youngest candidate at 37.

Moments after his interaction with the media, Mr Trump boarded the presidential helicopter and set off for Indianapolis, where he is due to give a speech at a National Rifle Association convention.