Microphones will be muted during the final US presidential debate to avoid Donald Trump and Joe Biden interrupting one another, it has been confirmed.
The new rules will mean Mr Trump and Mr Biden get two minutes to answer each question uninterrupted, the debate commission said on Monday.
The Trump campaign said the “last minute rule changes” had been made by a “biased commission in their latest attempt to provide advantage to their favoured candidate”.
The president also hit out at the moderator for the next debate, NBC’s Kristen Welker.
Mr Biden’s team have not yet commented.
The third and final TV debate will take place in Nashville, Tennessee on 22 October.
During a visit to Arizona for his fifth rally in three days on Monday, Mr Trump accused his Democratic rival of being a “criminal”.
Speaking to reporters beforehand he said: “Joe Biden is a criminal and he’s been a criminal for a long time.”
His comments are part of an ongoing bid by the Trump campaign to cast doubt over Mr Biden’s son Hunter’s business interests in Ukraine, which Trump claims have broken the law.
At the rally in Tucson, Mr Trump also launched another scathing attack on his top infectious diseases expert Dr Anthony Fauci.
He said: “People are tired of hearing Fauci and all these idiots…these people that have got it wrong.”
Describing Dr Fauci as a “disaster”, he said that “if we listened to him we’d have 700 to 800,000 deaths right now”.
Also using the opportunity to hit out at his rival, the president appeared to mock Mr Biden for “listening to the scientists”.
Responding on Twitter, the Democratic candidate said late on Monday: “@realDonaldTrump – if you had listened to the scientists it wouldn’t be this bad.”
Coronavirus has killed nearly 220,000 Americans so far, with Mr Trump widely criticised for his approach to the disease.
Dr Fauci said he was not surprised the president contracted the virus after he “saw him in a completely precarious situation of crowded, no separation between people, and almost nobody wearing a mask”.
Mr Biden, who is currently ahead in the polls, was not out on the campaign trail on Monday, but chose to stay in Delaware to prepare for Thursday’s debate.
His vice presidential candidate Kamala Harris returned to campaigning after seven days self-isolating following a positive COVID-19 result of a close adviser.