The potential disclosures to Anthony Pratt in April 2021 were passed on to special counsel Jack Smith's team after the billionaire then shared the information with dozens of foreign officials, employees and journalists, US outlet ABC News reported, citing anonymous sources.
The former president is being investigated for allegedly hoarding classified documents after leaving office.
The conversation was reported to the special counsel's team as part of this investigation, ABC News reported.
Australia, the US and the UK are working on a pathway for Canberra to acquire nuclear-powered submarines under the trilateral AUKUS pact.
The US outlet reported Mr Pratt was told about the number of nuclear warheads US submarines routinely carried and how they could get to a Russian submarine without being detected.
It's not clear if the information was accurate but it is being investigated and the businessman was reportedly told not to repeat the information.
Mr Pratt has been contacted for comment.
Opposition foreign affairs spokesman Simon Birmingham said the conversations happened before the Morrison and Biden governments finalised the AUKUS agreement so would not have spanned Australian measures undertaken to achieve the deal.
"There may have been ... hypotheticals about whether Australia should access American technology or submarines," he told Sky News on Friday.
"Of course, these are highly sensitive materials and information and it's why so much care needs to go into how we engage with the United States."
Former prime minister Scott Morrison unveiled the AUKUS agreement with US President Joe Biden and then UK prime minister Boris Johnson in September 2021.
The pathway to acquiring nuclear submarines was unveiled by Prime Minister Anthony Albanese in March this year.
Defence Minister Richard Marles has been contacted for comment.
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