A Georgia judge on Thursday dismissed three of the counts in the indictment accusing former US president Donald Trump and co-defendants of conspiring to overturn the results of the 2020 election in the southern state.

Two of the three charges thrown out by Fulton County Superior Court Judge Scott McAfee involved Trump, and he now faces a total of eight felony counts in Georgia.

McAfee declined, however, to quash the entire indictment, which accuses the Republican presidential candidate and his allies of racketeering and other offenses.

The three dismissed charges involved the filing of fake elector certificates with a federal court stating that Trump had won the election in Georgia, although he lost to Democrat Joe Biden by some 12,000 votes.

McAfee said that under the Supremacy Clause of the Constitution, state prosecutors cannot bring a case for federal crimes.

"The Supremacy Clause declares that state law must yield to federal law when the two conflict," the judge said in his order.

Trump had been charged with filing false documents and conspiring to file false documents.

The Georgia case has been frozen by an appeals court until it hears a bid by Trump and his co-defendants to disqualify Fani Willis, the Fulton County district attorney who brought the charges.

In March, McAfee rejected an attempt to disqualify Willis following revelations she had a romantic relationship with the man she hired as a special prosecutor.

Trump and his co-defendants appealed the ruling, and the Georgia Court of Appeals is to hear arguments in December.

Because the case is paused, the two counts against Trump of filing false documents will not technically be dropped until after the appeals court rules.

Evidence in the case includes a taped phone call in which Trump asked a top Georgia election official to "find" enough votes to reverse the result.

Eighteen co-defendants were indicted in Georgia along with Trump on racketeering and other charges, including his former personal lawyer Rudy Giuliani and ex-White House chief of staff Mark Meadows.

Four of Trump's original co-defendants, including three former campaign lawyers, have pleaded guilty to lesser charges in deals that spared them prison time.

Trump was convicted in a separate criminal case in New York in May of falsifying business records to cover up a hush money payment to a porn star who alleged they had a sexual encounter.

Trump is also facing federal charges of conspiring to overturn the 2020 election results, but no date has been set for a trial.