Trump had originally accepted the challenge, provided that proceeds from the event would go to charity, even stating that he would "love to debate Bernie," at a campaign rally in North Dakota on Thursday.

"He's a dream," the real estate magnate said. "If we can raise for maybe women's health issues or something. If we can raise $10 or $15 million for charity, which would be a very appropriate amount."

"I understand the television business very well. I think it would get high ratings," Trump continued.

The plan for the debate began on Wednesday evening, when Trump appeared on Jimmy Kimmel. During the interview, Kimmel read a note from the Sanders campaign inviting him to debate in California.