If President Donald Trump runs for re-election in 2020, a challenger may already be lined up: Dallas Mavericks owner and tech billionaire Mark Cuban.

In his appearance at New York's "OZY Fest," Cuban discussed challenging the president.

"If he lasts four years, I'll be there to kick his a**," Cuban said Saturday, before backpedaling a bit. "We'll see. I'm not making any proclamations yet."

Mark Cuban here at OzyFest on challenging Trump in 2020: “If he lasts four years, I’ll be there to kick his ass." — Steve Peoples (@sppeoples) July 22, 2017

Trump has shrugged off the notion of a President Cuban in the past, saying on Twitter that his fellow reality TV star wasn't up to the challenge.

I know Mark Cuban well. He backed me big-time but I wasn't interested in taking all of his calls.He's not smart enough to run for president! — Donald J. Trump (@realDonaldTrump) February 12, 2017

Resuming the war of words Saturday, Cuban took shots at Trump during a panel discussion with businessman Carlos Watson, comedian Samantha Bee and former Republican presidential candidate Jeb Bush.

Cuban was an outspoken critic of Trump during the campaign season, and Saturday's event wasn't the first time he's used a festival platform to slam the president and discuss a presidential bid.

At Austin's South by Southwest festival, Cuban called Trump the "Zoolander president," referring to the film starring Ben Stiller about a shallow and narcissistic male model. He also used the March festival to talk about running against Trump.

Cuban did not rule out a direct challenge to the Trump administration. "I've got a lot of time to decide and we'll see what happens," he said. But he said it's never been his dream to run for president or pursue politics.

Other public figures have their eyes on politics. Earlier this month, singer Kid Rock announced a bid for the U.S. Senate to challenge incumbent Democrat Debbie Stabenow of Michigan. Dwayne "The Rock" Johnson told GQ he wouldn't rule out running for president. Rapper Kanye West, comedian Chris Rock and actor Will Smith are also on the list of a handful of celebrities who have made comments about running for president.