Donald Trump is reversing course on debating Bernie Sanders before California's June 7 primary, saying in a statement that he would not be willing to debate a "second place finisher."

"Based on the fact that the Democratic nominating process is totally rigged and Crooked Hillary Clinton and Deborah Wasserman Schultz will not allow Bernie Sanders to win, and now that I am the presumptive Republican nominee, it seems inappropriate that I would debate the second place finisher," Trump said Friday afternoon.

He added: "As much as I want to debate Bernie Sanders -- and it would be an easy payday -- I will wait to debate the first place finisher in the Democratic Party, probably Crooked Hillary Clinton, or whoever it may be."

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The presumptive GOP nominee also trashed television networks as "not proving to be too generous" when it comes to donating to charitable causes, referring to the condition he laid down Thursday that at least $10 million must be forked over to charity before he would participate in a debate.

During a "Jimmy Kimmel Live" interview earlier this week, Trump said he'd be willing to debate the Vermont senator.

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 told reporters in North Dakota that he was indeed interested in debating.

"I'd love to debate him...Maybe if we can raise for women's health issues or something-- if we can raise ten or fifteen million for charity...," Trump said. "It should be in a big arena somewhere, and we can have a lot of fun with it."

Trump's reversal comes less than an hour after Sanders' own campaign announced the Vermont senator was ready to accept either of two television network offers to host the event.

"Our campaign and the Trump campaign have received two offers by broadcast television networks to host the Sanders-Trump debate that we suggested. Both offers include a major contribution to charity," said Jeff Weaver, Sanders' campaign manager, Friday in a statement. "We are prepared to accept one of those offers and look forward to working with the Trump campaign to develop a time, place and format that is mutually agreeable."