US President Joe Biden delivered a speech in Philadelphia on Thursday to highlight the release of his annual budget proposal.
In his speech, he referred to himself as "400 years old" and joked that he had only been around for a few years.
He also referred to former President Donald Trump as the "maybe future president," which caused the audience to boo.
Biden talked about a big fight he had with Trump when he was running for office, regarding the firing of inspectors general.
He said he had warned Trump not to do that, and now they were finding out that billions of COVID-19 relief dollars were stolen.
Biden is already the oldest US president at 80 years old.
He is set to face Donald Trump, 76, in the elections next year, although he has not announced his candidacy yet.
Biden declared that he had never been more optimistic about America's future than he is today.
The New York Post reported his remarks.
Biden also made a reference to a religious blessing when the audience booed his comments about Trump.