Donald Trump says he is pulling out of a scheduled September debate with U.S. Vice-President Kamala Harris on ABC and wants them to face off on Fox News, making it increasingly unlikely that the candidates will confront each other on stage before the November election.

In a series of Truth Social posts late Friday, the Republican nominee and former president said his agreement to a Sept. 10 debate on ABC "has been terminated" because he will no longer face Democratic President Joe Biden, who ended his campaign last month after a disastrous performance in their first debate.

Trump now says he will appear on Fox News on Sept. 4 in Pennsylvania with rules that he called "similar" to his debate with Biden, but with a full audience instead of a mostly empty studio. Trump said that if Harris, the likely Democratic nominee, does not agree to the new network and date, he will do a "major town hall" with Fox News.

Michael Tyler, a Harris spokesperson, said 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."

It was not immediately clear whether ABC would turn its Sept. 10 event into a Harris town hall in Trump's absence. Tyler said Harris is committed to the time slot and would appear "one way or the other to take the opportunity to speak to a prime time national audience."

In a subsequent Truth Social post on Saturday afternoon, Trump said of Harris, "I'll see her on Sept. 4 or, I won't see her at all."

Trump has gone back and forth on debating with Harris since she entered the presidential race. He had told reporters he felt an obligation to debate but also said in a recent Fox News interview that he thought Americans "already know everything" about both candidates Harris has pressed Trump to keep the commitment he made when Biden was in the race. Noting Trump's criticisms of her, Harris dared him recently to "say it to my face."

In his Truth Social posts, Trump also cited his litigation against ABC News as "a conflict of interest" in his participation in the network's debate. Trump sued the network in March following an assertion by anchor George Stephanopoulos that Trump had been found "liable for rape." A New York jury found Trump liable for sexually abusing advice columnist E. Jean Carroll but rejected her claim that she was raped.

But Trump agreed, two months after filing his lawsuit, to the Sept. 10 debate on ABC, as well as the June 27 debate on CNN that helped knock Biden out of the race. David Muir and Linsey Davis, not Stephanopoulos, are set to be ABC's debate moderators.

Trump has skipped debates before, including all the 2024 Republican presidential primary debates.