Former US President Donald Trump said on Tuesday he had received a letter from Special Counsel Jack Smith stating that he was a target of a grand jury investigation into efforts to overturn the 2020 presidential election result.

Smith "sent a letter (again, it was Sunday night!) stating that I am a TARGET of the January 6th Grand Jury investigation," Trump wrote on his Truth Social media site.

Trump did not provide evidence to support the assertion. A spokesman for Smith's office declined to comment.

Later on Tuesday, defense attorneys and federal prosecutors are due to make their first appearance in Florida before US District Judge Aileen Cannon, who is presiding over charges that he mishandled classified information and obstructed justice.

Trump, the front-runner for the Republican nomination to face Democratic President Joe Biden in the 2024 election, was charged last month with unlawfully retaining national defense documents after he left office in 2021 and conspiring to obstruct government efforts to retrieve them.

Smith is leading the prosecution also in that case.