A federal judge in Washington has formally postponed the March trial of former US president Donald Trump on charges of plotting to overturn the 2020 election, as a key legal appeal of his continues to work its way through the courts.

US District Judge Tanya Chutkan on Friday vacated the March 4 trial date in the case brought by Justice Department special counsel Jack Smith, but did not set a new one.

The move creates an opening for a separate case in New York, charging Mr Trump in connection with hush money payments to a porn actress, to proceed first.

The postponement comes as a federal appeals court has yet to resolve a pending appeal from Mr Trump arguing that he is immune from prosecution for actions he took in the White House.

It is not clear when the three-judge panel might rule, but a ruling in favour of prosecutors that permits the case to move forward is expected to be appealed against by the Trump team, probably resulting in additional delays.

For both sides, timing is of the essence.

Mr Trump, who faces four indictments and 91 felony counts, is looking to push his criminal cases back as he enjoys frontrunner status in the race for the 2024 Republican presidential nomination.

Smith’s team, meanwhile, is hoping to be able to prosecute Trump this year before the November election.

The Washington case had been expected to take place first, but it has been delayed for weeks by Trump’s appeal on immunity grounds.

The appeals court heard arguments on January 9, and though it had said it intended to work quickly, has not yet issued a ruling.