Former president Donald Trump shared classified information about US nuclear submarines with an Australian businessman shortly after he left office, in a meeting at his Florida private members club Mar-a-Lago, US media said Thursday.

The New York Times, citing unnamed sources, identified the businessman as billionaire Anthony Pratt, who heads one of the world's largest packaging companies.

ABC News, which first revealed the story, said Pratt later shared sensitive details about the US submarines with "scores of others, including more than a dozen foreign officials, several of his own employees, and a handful of journalists."

Sources told the Times that Trump's disclosures "potentially endangered the US nuclear fleet."

Federal prosecutors already investigating Trump for holding classified material at Mar-a-Lago after he left office, interviewed Pratt twice about the incident, the reports said.

Pratt may now be called by prosecutors to testify against Trump in his classified documents trial, which is due to start next May in Florida.

Pratt met Trump at his Palm Beach club in April 2021, and told the ex-president he thought Australia should start buying its submarines from the US, ABC reported.

In response, Trump allegedly told the businessman the exact number of nuclear warheads US submarines routinely carry, and precisely how close they can get to Russian submarines without being detected, the news outlet said.

Aside from the classified documents case, Trump faces three other indictments: one federal and one in Georgia over his efforts to overturn his election loss and stay in power, and one in New York stemming from election-eve hush money payments in 2016 to a porn star.

Trump is currently on trial in New York on charges of wildly and fraudulently inflating the value of his assets so as to get better terms from banks and insurance companies.