Donald Trump says he will wait to debate the official Democratic nominee, and not debate Bernie Sanders, calling the Democratic nominating process "totally rigged."

Trump said in a statement Friday that "it seems inappropriate that I would debate the second-place finisher," criticizing front-runner Hillary Clinton and the Democratic National Committee chairwoman Debbie Wasserman Schultz as "crooked."

"As much as I want to debate Bernie Sanders," Trump said, "I will wait to debate the first-place finisher in the Democratic Party."

Sanders responded with a statement of his own, saying, "Given that there are several television networks prepared to carry this debate and donate funds to charity, I hope that he changes his mind once again and comes on board."

Sanders added: "There is a reason why in virtually every national and statewide poll I am defeating Donald Trump, sometimes by very large margins and almost always by far larger margins than Secretary Clinton. There is a reason for that reality and the American people should be able to see it up front in a good debate and a clash of ideas."