Mark Cuban. Ezra Shaw/Getty Images Mark Cuban offered Donald Trump $10 million to let the billionaire businessman interview the Republican nominee for four hours about his policies.

Cuban, the owner of the NBA's Dallas Mavericks and star of ABC's "Shark Tank," presented the proposition in a scathing tweetstorm.

"$10mm to the charity of YOUR choice if you let ME interview you for 4 hrs on YOUR policies and their substance," Cuban wrote.

"Groundrules are that you can't mention the Clintons or discuss anything other than the details and facts of [your] plans and no one else is in the room to help," he continued. "Just me, you and a broadcast crew. Deal?"

Cuban said he would "add an option."

"If you need it, I'll write you the check and you can keep the money rather than give it to charity," Cuban posted. "In the immortal words of YOU. 'What do you have to lose?'"

His tweetstorm came in response to Trump's Friday morning interview with Fox Business host Maria Bartiromo, during which the Manhattan billionaire said Cuban was "really not smart enough" to understand Trump's economic plan.

Trump was responding to Cuban's claim that if the Republican nominee were to win in the fall, there would be "no doubt in my mind the markets tank."

Maria Bartiromo. Screenshot/Fox Business

"Well, I know Mark, and you know the problem with Mark is he's not smart enough to understand what we're doing," Trump said in the Friday interview. "He's really not smart enough."

"I've known him for a long time — he tweets me all the time," Trump said. "He sends me so many different tweets and calls me, although I must say not over the last number of months. Because I said this guy ... he'll send out so many tweets. I'll have to send you all of the Mark Cuban tweets and conversations."

Trump doubled down on Cuban being "not smart enough" to understand his economic plans, asking Bartiromo and her fellow Fox Business hosts to "explain to Mark" that "we're in trouble."

"He's a mixed-up guy," Trump said.

In an interview with Business Insider this week, Cuban said he couldn't "think of anybody more dangerous as president than Donald Trump."

"You've never heard me talk about politics all that much, and it's just — I can't think of anybody more dangerous as president than Donald Trump," he said. "I can't think of anything worse than with him not having a clue. I mean, could you imagine somebody who doesn't read and doesn't learn trying to deal with the day-to-day changes and challenges of that job?"

Cuban endorsed Democratic nominee Hillary Clinton at a rally in Pittsburgh, his hometown, in July. Cuban has ripped Trump repeatedly on social media in recent months, after souring on the Manhattan billionaire's candidacy.