An audio recording in which Donald Trump appears to acknowledge keeping a classified document after leaving the White House has been obtained by US media.

In the recording, the former president is heard riffling through papers and saying: "This is highly confidential."

It was first obtained by CNN, but the BBC's US partner CBS also has the clip.

Mr Trump has pleaded not guilty to federal charges of mishandling sensitive documents.

CNN was the first to publish the roughly two-minute recording, which it said came from a July 2021 meeting at Mr Trump's Bedminster, New Jersey golf club between him and several people working on the memoir of his former chief of staff Mark Meadows.

Mr Trump is heard saying "these are the papers" and referring to a document he calls "highly confidential".

"This was done by the military and given to me," he says. "See as president I could have declassified it. Now I can't, you know, but this is still a secret."

It appears to be the same audio recording cited by federal prosecutors in their indictment of Mr Trump.

It is not clear from the indictment, however, if the documents referenced in the recording were ever recovered by investigators.

Prosecutors allege the former president showed classified documents to people without security clearance on two occasions, including a writer and two members of staff.

Mr Trump is facing 37 counts of illegally retaining classified documents and obstructing the government's efforts to get them back.

He has repeatedly denied wrongdoing.

He has said all the documents he took with him from the White House were declassified, but the published audio recording appears to contradict this.

In an interview last week with Fox News, the former president denied that he showed secret documents to people unauthorised to view them in the Bedminster meeting.

"There was no document. That was a massive amount of papers and everything else talking about Iran and other things," Mr Trump said, adding that he was presenting "newspaper stories, magazine stories and articles".

The recording, however, appears to suggest that Mr Trump was referencing specific files.

He was indicted alongside an aide, Walt Nauta, who is expected to plead not guilty at a hearing on Tuesday.

The former president's trial is scheduled for 14 August but that is likely to be delayed. A judge is yet to rule on a motion from prosecutors seeking to delay it until 11 December.