Donald Trump threatens to pull out of 10 September presidential debate

Donald Trump has expressed doubt that he will participate in a scheduled televised debate with Kamala Harris next month, hurling a trademark “fake news” slur at the network that had agreed to host it.

The former president and Republican nominee threatened to pull out of the 10 September meeting with Harris , the vice-president and Democratic nominee for November’s election, in a post on his Truth Social network on Sunday night.

Referring to an interview on ABC’s This Week earlier in the day with the host Jonathan Karl and the Republican Arkansas US senator Tom Cotton, Trump questioned the network’s fairness for the only debate that both presidential candidates had already agreed on .

Related: Fears within Trump campaign that palace intrigue could cause distraction

“I watched ABC FAKE NEWS this morning, both lightweight reporter Jonathan Carl’s(K?) ridiculous and biased interview of Tom Cotton (who was fantastic!), and their so-called Panel of Trump Haters, and I ask, why would I do the Debate against Kamala Harris on that network?” Trump wrote with his usual penchant for erroneous upper case letters.

He also alluded to his ongoing defamation lawsuit against the This Week host George Stephanopoulos and the ABC network over comments the anchor made in March stating Trump had been found “liable for rape” instead of sexual abuse in a case brought by the New York writer E Jean Carroll.

It is not the first time that Trump, who trails Harris by seven points nationally in a new Fairleigh Dickinson University poll published on Saturday, has sowed doubt over his debate appearance.

“Right now I say, why should I do a debate? I’m leading in the polls. And, everybody knows her, everybody knows me,” he told Maria Bartiromo on Fox Business Network earlier this month after Harris replaced Joe Biden at the top of the Democratic ticket.

He stated he had pledged instead to take part in a 4 September debate on Fox News, to which the Harris campaign did not agree, saying he would see Harris there “or not at all”, before changing his mind again.

Harris, meanwhile, seized on Trump’s wavering commitment before a lively crowd at a rally in Atlanta, Georgia, last month. “If you got something to say, say it to my face,” she said.

Trump’s latest hesitation comes amid a reported impasse between the two presidential campaigns over the conditions of next month’s debate. Politico cited four sources on Monday claiming that negotiations had broken down over the turning off of the participants’ microphones when it was not their turn to speak.

According to the report, the Harris campaign is demanding that the microphones be left “hot” at all times, in the apparent belief that the vice-president can make Trump lose his cool under questioning and utter something damaging or inappropriate.

Trump’s campaign, meanwhile, has been pressing for them to be turned off.

“We have told ABC and other networks seeking to host a possible October debate that we believe both candidates’ mics should be live throughout the full broadcast,” Brian Fallon, senior adviser for communications for the Harris campaign, told Politico in a statement.

“Our understanding is that Trump’s handlers prefer the muted microphone because they don’t think their candidate can act presidential for 90 minutes on his own. We suspect Trump’s team has not even told their boss about this dispute because it would be too embarrassing to admit they don’t think he can handle himself … without the benefit of a mute button.”

On Monday, Trump appeared to undercut his campaign’s position by declaring he would prefer to have the microphones on.

“I’d rather have it probably on, but the agreement was that it would be the same as it was last time. In that case, it was muted. I didn’t like it the last time, but it worked out fine,” he told reporters.

Trump’s campaign had insisted Harris was reneging on terms agreed for the debate by the Biden campaign when it accepted the 10 September date – and another meeting on CNN in June that never took place.

Conditions for those debates included the turning off of microphones between exchanges, as was traditional in debates during previous presidential campaigns.

“Enough with the games,” Jason Miller, a Trump senior adviser, told Politico in a statement on Sunday.

“We accepted the ABC debate under the exact same terms as the CNN debate. The Harris camp, after having already agreed to the CNN rules, asked for a seated debate, with notes, and opening statements. We said no changes to the agreed upon rules.”

The Harris campaign disputed the accuracy of Miller’s statement, as well as his assertion that it was Harris seeking to withdraw from the debate – and not Trump.

“This seems to be a pattern for the Harris campaign. They won’t allow Harris to do interviews, they won’t allow her to do press conferences, and now they want to give her a cheat-sheet for the debate. My guess is that they’re looking for a way to get out of any debate with President Trump,” he said.

The dispute comes as the Trump campaign seeks ways to blunt significant momentum built by Harris since she became the Democratic nominee, including a surge in both polling and donations .

On Monday, the Guardian reported growing fears among the former president’s senior staff that “palace intrigue” over its leadership could distract from the urgency of regaining a solid footing in the race with little more than 10 weeks until the 5 November polling day.