The day after former Vice President Joe Biden formally entered the 2020 presidential primary field, President Donald Trump took a dig at Biden's age and jokingly called himself "a young, vibrant man."

Trump, 72, currently holds the record as the oldest person to take the office of the presidency at 70 years and 220 days old, but Biden, currently 76, could break his record.

" I look at Joe, I don't know about him. I don't know. I would never say anyone is too old. I know they are all making me look very young both in terms of age and I think in terms of energy," Trump said.

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The day after former Vice President Joe Biden formally entered the 2020 Democratic presidential primary field, President Donald Trump took a jab at Biden's age and jokingly called himself "a young, vibrant man."

Trump, 72, currently holds the record as the oldest person to take the office of the presidency at 70 years and 220 days old on Inauguration Day 2017.

But Biden, currently 76, and fellow Democratic contenders Sen. Bernie Sanders, 77, and Sen. Elizabeth Warren, 69, could break his record.

If elected, Biden would be 78 years and 61 days old on Inauguration Day 2021. That would also break Ronald Reagan's record for the oldest president at any point in a presidency. Reagan was 77 years and 349 days old when he departed office.

"I think that I feel like a young man. I'm so young. I can't believe it. I'm the youngest person — I'm a young, vibrant man," Trump joked to reporters on the White House's South Lawn before departing on Air Force for an NRA convention in Indiana.

"I look at Joe, I don't know about him. I don't know. I would never say anyone is too old. I know they are all making me look very young both in terms of age and I think in terms of energy," Trump added.

Read more: A day after his 2020 launch, Trump is acting like Joe Biden is his real competition for the presidency

Trump views Biden, who served as President Barack Obama's Vice President for eight years and a US Senator for 36, as the biggest threat to his re-election chances and peppers his aides with questions about Biden's strength as a nominee, according to a new report in Politico.

Unlike other Democratic contenders, Biden centered his initial announcement not on any particular policy issues or why he was uniquely suited to lead, but on directly attacking Trump and the urgent need to defeat him.

"Welcome to the race Sleepy Joe," Trump tweeted Thursday after Biden formally entered the race. "I only hope you have the intelligence, long in doubt, to wage a successful primary campaign...but if you make it, I will see you at the Starting Gate!"