The apparent agreement came after Trump appeared on Jimmy Kimmel Live! Kimmel read a question submitted by Sanders himself, in which the Vermont senator asked whether Trump would fill in for Hillary Clinton in what was supposed to be a Democratic primary debate ahead of the June 7 California primary.
"Hillary Clinton backed out of an agreement to debate me in California before the June 7 primary, are you prepared to debate the major issues facing our largest state and the country before the California primary, yes or no?" read Sanders' question.
"Yes I am, how much is he going to pay me?" Trump said. "Because if I debated him, we would have such high ratings, and I think I should take that money and give it to some worthy charity."
Sanders quickly seized on the response on Twitter, sparking the #BernieTrumpDebate hashtag.
As of Thursday morning, it was unclear whether the debate would actually take place.
And a report from CBS News said Trump was joking, and a debate will not happen.