Hillary Clinton Hillary Diane Rodham ClintonJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Momentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina MORE is dismissing talks of a presidential debate between Bernie Sanders Bernie SandersNYT editorial board remembers Ginsburg: She 'will forever have two legacies' Two GOP governors urge Republicans to hold off on Supreme Court nominee Sanders knocks McConnell: He's going against Ginsburg's 'dying wishes' MORE and Donald Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE.

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"I don't think it's going to happen," the Democratic front-runner said Thursday during a call-in to "Meet the Press Daily" on MSNBC. "You know, I know they've gone back and forth on this, and they seem to be saying it's some kind of joke. Trump doesn't sound very serious."

"But I can tell you, I look forward to debating Donald Trump in the general election. I can't wait to get on that debate stage with him."

The Sanders and Trump campaigns are reportedly engaged in "back-channel conversations" to arrange a debate for the two presidential candidates after Trump said on ABC's "Jimmy Kimmel Live" Wednesday he'd be open to it.

Trump then told reporters Thursday Sanders is "a dream" and he would love to debate him.

“So what we can do, if we can raise for maybe women’s health issues or something — if we can raise 10 or 15 million dollars for charity, which would be a very appropriate amount. I understand the television business very well.”

Sanders's campaign manager Jeff Weaver said Thursday a debate would "benefit voters from across the country."

"I have to believe it would be one of the most-watched debates in presidential politics," Weaver told MSNBC.

Clinton dismissed the proposed debate again minutes later during a phone interview with CNN anchor Wolf Blitzer.

“Oh Wolf, this doesn’t sound like a serious discussion,” she said. “I’m looking forward to debating Donald Trump in the general election. I can’t wait to get on the stage with him.”

Asked again for her reaction to the idea of Sanders and Trump getting on stage together, Clinton replied, “I just said I don’t think it's serious. I think it’s not going to happen."

A debate between Trump, the de facto GOP presidential nominee, and Sanders, who trails Clinton in the race for the Democratic nomination, while the primaries are still ongoing would be unprecedented.

—Elliot Smilowitz contributed.