Federal prosecutors have obtained a recording of former President Donald Trump discussing a sensitive military document he took with him after leaving the White House, a potentially damaging piece of evidence in the ongoing investigation of his handling of classified documents, multiple outlets reported Wednesday.

CNN , citing people familiar with the tape, first reported that investigators had obtained a recording from a July 2021 meeting in New Jersey between Trump and several people working on a memoir by his former chief of staff, Mark Meadows. The New York Times reported that one of Trumps aides, Margo Martin, regularly recorded interviews he gave for books.

During the conversation, Trump reportedly referenced a document that he said had been compiled by the chairman of the Joint Chiefs of Staff, Gen. Mark Milley, related to the U.S. attacking Iran, which he apparently still had in his possession.

Trump later indicated that he knew the document was secret, according to the Times.

The revelations could undermine the claims Trump has used to defend himself in the ongoing investigation. Justice Department special counsel Jack Smith is reportedly nearly finished collecting testimony and evidence in the probe, which began after a monthslong effort to recover boxes of classified documents from the former presidents Mar-a-Lago resort in Florida.

Smiths team has been homing in on whether Trump attempted to obstruct the governments efforts to recover the documents and violated any laws related to classified material.

Trump has vehemently defended his post-White House behavior, saying at times that he had a standing order to automatically declassify documents removed from the Oval Office. During a CNN town hall-style event earlier this month, he appeared to claim he was allowed to take anything he wanted when he left the White House, saying: I took the documents; Im allowed to.

He also said he was entitled to show classified documents to others after his presidency, although Trump said he hadnt done so.

Not really, Trump said during the event. I would have the right to. By the way, they were declassified after.

The Times reported that Meadows autobiography also appears to reference an Iran-related document at the same July 2021 meeting, including a passage where Trump recalls a four-page report typed up by Mark Milley himself.

It contained the generals own plan to attack Iran, deploying massive numbers of troops, something he urged President Trump to do more than once during his presidency, the book reads.

A spokesman for Trump called the investigation political persecution in a statement to the Times, adding that the probe was designed to inflame tensions and continue the medias harassment of President Trump and his supporters.