An ally of Donald Trump has pleaded guilty to conspiring to interfere with Georgia’s elections as part of the former US president’s attempts to overturn his 2020 defeat.

Former Republican poll watcher Scott Hall is so far the only one of 19 defendants, including Trump, to plead guilty in Fulton County, Georgia’s conspiracy case, one of four criminal prosecutions that have ensnared the frontrunner for the 2024 Republican nomination.

A live video of a court proceeding on Friday showed Hall pleaded guilty to five counts of conspiracy to commit intentional interference with the performance of election duties, a misdemeanour charge.

The plea agreement calls for Hall to be sentenced to five years of probation and pay a $US5000 ($A7800) fine, a prosecutor said at the hearing.

He will also be required to testify against other defendants in the case.

Lawyers for Hall did not immediately return requests for comment.

Hall, a Georgia bail bondsman, initially faced charges of racketeering as well as conspiracy to commit election fraud and computer crimes. He was accused of taking part in an unlawful breach of voting equipment in rural Coffee County in the southeastern part of the state in January 2021.

Former Trump lawyer Sidney Powell, one of two defendants set to stand trial beginning next month, is also accused of taking part in the breach. Powell has pleaded not guilty.

Trump has denied wrongdoing and said the case is part of a political witch hunt.

The former president faces criminal charges in four cases. He is also under indictment in Florida for his handling of classified documents after leaving office, in Washington for his efforts to overturn the 2020 election and in New York over hush money paid to pornographic actress Stormy Daniels before the 2016 election.

Trump has denied wrongdoing and pleaded not guilty in those cases as well.

-AAP