Donald Trump's Georgia trial on charges of trying to overturn his 2020 election defeat will not begin in October, a judge says in a ruling that will allow the former US president to be tried after two of his former lawyers.

Fulton County Superior Court Judge Scott McAfee cited logistical concerns and the array of unsettled legal issues in separating the trial of lawyers Kenneth Chesebro and Sidney Powell from Trump and the other 16 co-defendants.

A trial date for Trump, the front-runner for the 2024 Republican presidential nomination, has not yet been set and the judge indicated the case may have to be split up further.

McAfee previously voiced skepticism that all 19 defendants could be tried together.

Trump was charged in August in an indictment alleging he and his co-defendants conspired to pressure Georgia election officials to reverse his loss to Democratic President Joe Biden.

Trump and the other defendants have pleaded not guilty.

Powell and Chesebro, two lawyers accused of aiding Trump's efforts to reverse his election defeat, previously asked for a speedy trial, which is scheduled to begin on October 23.

Trump and several other defendants said that timeline would not give them enough time to prepare a defence.