Former US President Donald Trump allegedly shared classified information about US nuclear submarines with an Australian businessman in April 2021, after leaving the White House.

ABC television on Thursday quoted sources as saying the former president may have revealed the sensitive information during a meeting with the Australian at Trump's Mar-a-Lago estate in Florida.

Trump allegedly mentioned the supposed number of nuclear warheads that US submarines routinely carry and how close they can supposedly get to Russian submarines without being detected.

ABC News reported that authorities have interviewed the businessman.

Trump's spokesperson said he has always acted according to the law.

Trump was indicted in June for illegally retaining documents, including those with highly classified information, at his home after leaving office.

US media outlets are once again focusing on Trump's handling of sensitive information as he plans to seek reelection next year.