Mark Cuban laid down the gauntlet in his ongoing back-and-forth with Donald Trump Friday. The Shark Tank star and Dallas Mavericks owner made a $10 million for a four-hour interview with the candidate.

Cuban took to Twitter midday Friday to offer a major donation to the charity of Trump's choice in exchange for a televised discussion of the candidate's policies and their substance. In a five-part tweet storm, he laid out the ground rules of the proposal, including no mention of discussion of Bill and Hillary Clinton and no one else in the room.

He also added in a dig at Trump's wealth. "If you need it, I'll write you the check and you can keep the money rather than give it to charity," he wrote.

1) @realDonaldTrump $10mm to the charity of YOUR choice if you let ME interview you for 4 hrs on YOUR policies and their substance.

— Mark Cuban (@mcuban) September 16, 2016

2) @realDonaldTrump groundrules are that you cant mention the Clintons or discuss anything other than the details and facts of yr plans and

— Mark Cuban (@mcuban) September 16, 2016

3) @realDonaldTrump and no one else is in the room to help. Just me, you and a broadcast crew.

Deal ?

— Mark Cuban (@mcuban) September 16, 2016

4)@realDonaldTrump I'll 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

— Mark Cuban (@mcuban) September 16, 2016

5) @realDonaldTrump In the inmortal words of YOU. "What do you have to lose ?"

— Mark Cuban (@mcuban) September 16, 2016

Cuban has become one of Trump's premier trolls as of late.

He has cast doubt onto the real estate magnate's claims of wealth, called into question his mental health, bashed his business skills and challenged his understanding of the issues. As he endorsed Hillary Clinton for the presidency in July, he called Trump a "jagoff."

Cuban most recently took a swipe at the GOP nominee's son, Eric Trump, pointing out he had shared a false photo of his father's rally in Florida. "I'm pretty sure that's our arena in Dallas eric," Cuban pointed out.

I'm pretty sure that's our arena in Dallas Eric. #WrongBasket https://t.co/rh8WGWuDO0

— Mark Cuban (@mcuban) September 10, 2016

Earlier in the day Friday, Trump made a dig of his own at Cuban while speaking with Fox Business' Maria Bartiromo, saying "he is not smart enough to understand what we are doing." Cuban hit back on that on Twitter, too.

Trump goes after @mcuban today: "The problem with Mark, he is not smart enough to understand what we are doing." pic.twitter.com/EtukVgV8Fp

— Sopan Deb (@SopanDeb) September 16, 2016