WASHINGTON — Dallas billionaire Mark Cuban said Friday that he was personally approached for help by someone who wanted to pay Donald Trump to drop out of the presidential race.

Cuban was asked earlier in the day by reporters on Hillary Clinton's campaign plane if the Koch brothers, major Republican donors, had attempted to bribe Trump to leave the GOP primaries. "They tried," he said, though he later clarified that he didn't mean the Kochs were involved.

The reason Trump did not accept the deal, Cuban said, was that they "didn't offer him enough."

Cuban told The Dallas Morning News in an email that "someone" tried to recruit him to make a Trump offer.

"I had discussion about a Trump buyout," Cuban wrote. "That's as much as I can tell u."

Trump campaign officials did not immediately respond to a request for comment.

Cuban declined to say who was involved and said he didn't ask many questions about the idea. He would not say how much the offer was intended to be.

The discussions were held shortly after the Democratic National Convention in July, Cuban said, "when [Trump's] numbers were way down." Cuban said he could not confirm that an offer was made because he was not there, but he said he got the information from someone he trusts.

Businessman and investor Mark Cuban spoke to reporters on Democratic presidential nominee Hillary Clinton's campaign plane while flying to Detroit on Friday. (Brendan Smialowski/Agence France-Presse)

"Supposedly an amount was presented to Trump and he said no," he said, adding that the proposal "sure seemed serious."

The Dallas Mavericks owner and Shark Tank star described the offer as a "buyout," pushing back on the notion that it constituted a bribe.

"The word bribe was never used," he wrote. "It was a buyout. That's the way it was discussed."

Cuban, who has been a constant thorn in Trump's side over the closing months of the campaign, was stumping with Clinton on Friday in Pittsburgh and Detroit.

Steve Lombardo, a spokesman for Koch Industries, denied any suggestion that the Koch brothers were involved in attempting to bribe Trump to drop out of the race.

"The statement is absolutely false," Lombardo said. "That did not happen."

Dallas investor Doug Deason, a GOP mega donor and Trump supporter, said he has known Cuban for many years and cautioned against reading too much into his claims.

"Take anything that he says and discount it by 200 percent to get close to the truth," Deason said. "He is totally irrelevant to this election."

Staff writer Katie Leslie contributed to this report.