Trump documents: Congress offered briefing on records kept at Mar-a-Lago

The precise nature of the briefing remains unclear. The offer from the justice department and the Office of the Director for National Intelligence (ODNI) was described as unofficial on Sunday and no date had yet been set, though the briefing could come as soon as this week.

The nature of the documents is one of the central issues in the criminal investigation into Trump overseen by the special counsel Jack Smith, who is examining whether the former president wilfully retained national security information and obstructed justice.

Biden and Pence have cooperated with authorities, over cases involving vastly fewer documents than were retained by Trump, who has not offered such cooperation.

Republicans in Congress have seized on the discovery that Biden retained documents as a means to pressure the president and his administration.

Since the FBI searched Mar-a-Lago on 8 August last year and seized 101 classified-marked documents, Trump has claimed the papers were declassified, though no such evidence has emerged and his lawyers have not repeated that assertion in court, where they face penalties for lying.

Investigators have focused on the matter and last year granted immunity to a top Trump ally, Kash Patel, in an effort to force him to testify before a grand jury about the declassification claims. Patel initially invoked his fifth amendment right against self-incrimination.

Justice department interest in Patel centered on his claims that the documents found at Mar-a-Lago were declassified, how the documents ended up at the property, and how Trump and his team responded to requests for their return, the Guardian previously reported.