Donald Trump plans to debate Biden on Oct 24 despite 'unfair' rule changes

US President Donald Trump has confirmed his participation in the presidential debate with his Democratic challenger Joe Biden later this week, even as he raised objections about "unfair" changes in the format.

Trump, 74, and Biden, 77, are slated to face their final presidential debate at Belmont University in Nashville, Tennessee on October 22.

The non-partisan Commission on Presidential Debates (CPD) on Monday announced new rules under which it will mute microphones for two minutes of the rival speakers so as to give them uninterrupted opening remarks.

"I'll participate, I just think it is very unfair, Trump told reporters aboard Air Force One on Monday.

"I will participate, but it's very unfair that they changed the topics and it is very unfair that again we have an anchor who is totally biased," the president said, responding to a question on changes in the debate rules by CPD.

In a letter to CPD on Monday, Trump 2020 campaign manager Bill Stepien expressed concern over the announced topics for what was always billed as the 'Foreign Policy Debate' in the series of events agreed to by both the Trump and the Biden campaigns many months ago.

"The topics announced by moderator Kristen Welker (fighting COVID-19, American families, race in America, climate change, national security, and leadership) are serious and worthy of discussion, but only a few of them even touch on foreign policy, he said, asserting that almost all of the topics were discussed at length during the first debate "won" by Trump.

Under the new rules, Trump and Biden will each have two minutes of uninterrupted time to speak at the beginning of every 15-minute segment of the debate

"The only candidate whose microphone will be open during these two-minute periods is the candidate who has the floor under the rules," the commission said in a statement on Monday.

"For the balance of each segment, which by design is intended to be dedicated to open discussion, both candidates' microphones will be open," it said.

The commission said both campaigns have agreed to the two-minute, uninterrupted rule.

The decision to mute microphones comes after a chaotic first presidential debate that saw the two candidates interrupting each other repeatedly.

The September 29 debate, moderated by Fox News anchor Chris Wallace, was widely criticised for its off-the-rails nature.

The second presidential debate set for October 15 was cancelled after Trump refused to do a virtual face-off with his Democratic challenger despite concerns over his COVID-19 diagnosis. The presidential rivals separately held competing town halls last week instead.

The third and final debate will be moderated by NBC News correspondent Kristen Welker.