President Donald Trump, fresh from a round of diplomacy with Japan's prime minister, renewed a feud with billionaire Mark Cuban on Sunday, a familiar foil with whom he's sparred in the past.

As the world grappled with North Korea's latest act of aggression —firing off a new ballistic missile—Trump harangued the outspoken investor in a series of early morning tweets. Along with defending his crackdown on immigration, Trump blasted Cuban as being "not smart enough" to be leader of the free world.

Trump tweet

The president also took a swipe at recent court decisions that dealt stinging blows to his travel ban, which he insists is necessary for national security purposes.

Trump travel ban

For his part, Cuban —who supported Democratic contender Hillary Clinton in the general election—dismissed the broadside with a simple "LOL". However, Cuban then tweeted an image of a 2016 letter he wrote to Trump, offering him support while imploring him to master the issues he would face as president.



Cuban tweet

It wasn't immediately clear why Trump lashed out at Cuban, seemingly without provocation, but the two billionaires have a lengthy and checkered history of exchanging trash talk.

At the height of the general election, the Dallas Mavericks owner was once approached by a group of dissident Republicans to run as an independent candidate, a move Cuban ultimately ruled out. Trump has made sport of name-calling Cuban on social media, at one point referring to him as "dopey." Cuban often downplays Trump's insults, or responds with thinly veiled criticism.

Cuban retort