Vice President Kamala Harris and Republican presidential nominee Donald Trump took turns insulting each other Saturday over a weekslong dispute about when and where they would debate each other.

The former president has refused to agree to a previously scheduled Sept. 10 debate hosted by ABC News. He has instead tried to pressure Harris, the de facto Democratic presidential nominee, to accept an earlier debate in a vastly different setting on Trump friendly Fox News.

Trump on Friday announced on Truth Social that he had agreed with Fox News to do a Sept. 4 debate against Harris with Fox News moderators and a full audience in attendance.

The Harris campaign on Saturday mocked Trump for walking back his commitment to the ABC News debate.

“Donald Trump is running scared and trying to back out of the debate he already agreed to and running straight to Fox News to bail him out,” Harris campaign spokesman Michael Tyler said, in a statement on Saturday.

Trump cited ongoing litigation with ABC News as creating a “conflict of interest.” Fox News did not immediately respond to a request for comment.

“He needs to stop playing games and show up to the debate he already committed to on Sept 10. The Vice President will be there one way or the other to take the opportunity to speak to a prime time national audience,” Tyler said.

Later, Trump fired back in several Truth Social messages, calling Harris a “low I.Q. individual.”

“Kamala Harris doesn’t have the mental capacity to do a REAL Debate against me, scheduled for September 4th in Pennsylvania,” Trump wrote in another Truth Social post. “I’ll see her on September 4th or, I won’t see her at all.”

President Joe Biden and Trump in May agreed to two debates on mutually accepted terms, one hosted by CNN on June 27 and the second by ABC News on Sept. 10. Though Biden has since exited the race due to his own disastrous debate performance in June, the Harris campaign has maintained that the terms of the May deal still hold.

Days after Biden dropped out and endorsed Harris, Trump said he would be willing to debate the vice president multiple times. As Harris has gained in the polls and hauled in record fundraising, Trump has repeatedly walked back that initial May agreement and teased the idea of skipping the debates altogether.

The Harris campaign has said that the vice president will show up at the Sept. 10 debate whether Trump is there or not.

“It’s interesting how ‘any time, any place’ becomes ‘one specific time, one specific safe space,'” Harris wrote in an X post on Saturday, doubling down. “I’ll be there on September 10th, like he agreed to. I hope to see him there.”