Donald Trump claimed presidents can "declassify anything" simply by "thinking about it", in his first television appearance since the FBI seized top secret documents from his Florida home.
The former US president said he had recently discovered the FBI had also seized his will during the raid last month, accusing the bureau of doing a "horrible thing".
The unprecedented FBI raid led to 11,000 government records, including about 100 marked classified, being recovered from Mar-a-Lago, Mr Trump's private members' club and his primary residence.
In his first television interview since, Mr Trump, 76, insisted that he had "declassified everything" he took from the White House after leaving office.
“There doesn’t have to be a process, as I understand it," he told Fox News.
"If you're the president of the United States you can declassify just by saying: 'It's declassified.' Even by thinking about it.
"You're the president, you make that decision."
He added: "I declassified everything."
Presidents do have the authority to declassify information, but this typically follows a process to ensure there are no associated security risks.
Former officials in the Trump administration have scoffed at the notion that the Republican leader could have issued a blanket order.
Bill Barr, Mr Trump's former attorney general, has previously said the suggestion was "almost worse than taking the documents".
"If in fact he sort of stood over scores of boxes, not really knowing what was in them and said: 'I hereby declassify everything in here,' that would be such an abuse,” said Mr Barr.
"And that shows such recklessness, it's almost worse than taking the documents.”
According to The Washington Post, the details of the nuclear defences of an unnamed foreign country were among the documents FBI agents seized from Mar-a-Lago.
In his interview, Mr Trump defended storing documents at Mar-a-Lago, where he often entertains visitors.
Mr Trump pointed out that the property is manned by Secret Service agents, making a rare reference to himself as a former president. He has refused to concede his defeat to Mr Biden in the 2020 election.
"I think we had good security. As you know, we had a tremendous Secret Service. They are unbelievable people. And they are all over Mar-a-Lago, as happens to a former president," he said.
He went on: "I hate to use the word 'former,' because I have a lot of problems with what happened."
Mr Trump also suggested it was the General Services Administration that dealt with packing the boxes that went from the White House to Mar-a-Lago.
The agency refuted that claim on Thursday, insisting it was only involved in shipping the boxes and was not aware of their contents.
At another point, Mr Trump described his shock at learning of the raid on Mar-a-Lago.
The former president said his lawyers had been having "very nice discussions" about the return of documents with government officials.
“All of a sudden we got hit very hard by the FBI," he said.
"They took a lot of things. I think they took my will. I found out yesterday,” he said, joking that its publication “could cause a lot of problems”.
The pre-recorded interview came ahead of a US appeals court ruling allowing the FBI to use the seized documents in its ongoing criminal probe.
The ruling was a major setback for Mr Trump, who had sought an injunction that could have delayed the FBI's investigation by weeks.
In the ruling, the judges rejected the possibility that Mr Trump could have an "individual interest in or need for" the 100 documents marked classified.
The three-judge panel pointedly noted that the former president had presented no evidence that he had declassified the top secret records, as he has claimed publicly.