WASHINGTON, Aug 26, 2024 (BSS/AFP) - A much-anticipated US presidential debate next month appeared in doubt Monday as Republican candidate Donald Trump questioned whether he would participate, and both camps sparred over the use of live mics.

Trump had already balked at participating in the September 10 showdown with Democratic candidate Kamala Harris, amid ongoing quibbles.

On his Truth Social media platform Sunday, Trump accused TV broadcaster ABC of bias, posting: "I ask, why would I do the Debate against Kamala Harris on that network?

Harris's campaign Monday said that the two camps were locked in disagreement over whether each candidate's mic would be muted when the other spoke.

During a June 27 debate on CNN between Trump and President Joe Biden, who was the Democratic candidate at that time, microphones were turned off when it was not a candidate's turn to speak.

It was a condition negotiated by Biden, and one that was meant to apply to the September debate on ABC as well.

But Harris, who replaced Biden after his disastrous performance at the CNN debate, prefers a return to the norm of keeping microphones on.

"We believe both candidates' mics should be live throughout the full broadcast," Harris communication director Brian Fallon said in a statement.

He alleged that "Trump's handlers prefer the muted microphone because they don't think their candidate can act presidential for 90 minutes."

The Trump camp said the debate should occur under the already agreed conditions.

"Enough with the games. We accepted the ABC debate under the exact same terms as the CNN debate," Jason Miller, senior advisor for Trump, told Politico.

The Harris campaign believes a mics-on debate could create opportunity for Trump to lose his temper or make off-color remarks, according to Politico.

Harris and Trump are neck and neck in the polls two weeks before the debate, which is scheduled to be held in Philadelphia.