Fox News is in back-channel negotiations for an event featuring Donald Trump and Bernie Sanders before California's June 7 primary, according to Fox News anchor Bret Baier.

"It is not a joke and those back channel discussions are continuing and there will be some event in California," he said on "Special Report with Bret Baier" Thursday.

In a Friday interview with WMAL's Brian Wilson, Baier said that the talks with the two campaigns "are progressing" and that there's "real interest."

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The details, he added, were still being hammered out, but it would either be a "full-blown debate" or perhaps something in a town hall format.



This comes soon after Trump first agreed during a "Jimmy Kimmel Live" interview that he would debate with the Vermont senator.

At the time, Trump had said he would participate in a forum if the proceeds would go to charity. After Sanders sent out a tweet declaring "Game on," however, Trump's campaign seemed to suggest that the presumptive GOP nominee was joking. But on Thursday, Trump reiterated his interest in debating, provided the funds go to a philanthropic cause.

When asked about the price tag Trump has demanded for the debate -- at least $10 million to be donated to charity -- Baier said that they are "working that out."

"It won't be from the network," he added, but "there are multiple conversations going on."

Baier said that Hillary Clinton, the current Democratic front-runner, "also is invited to this but is not interested."

He noted Clinton turned down the solely Democratic primary debate proposed by Fox News and the Sanders campaign earlier this month.