US Attorney General Merrick Garland said on Thursday he had "personally approved" the dramatic raid on Donald Trump's Florida home and, in a highly unusual move, was requesting the warrant justifying the search be made public.

The country's top prosecutor did not reveal the reason for the unprecedented search of the residence of a former American president, and condemned "unfounded attacks" on the FBI and the Justice Department that followed it.

"I personally approved the decision to seek a search warrant," Garland told reporters. "The department does not take such a decision lightly."

"The search warrant was authorised by a federal court upon the required finding of probable cause," he said.

While noting that "ethical obligations" prevented him detailing the basis of the raid, Garland said he had asked a Florida judge to unseal the warrant because Trump had publicly confirmed the search and because of the "substantial public interest in this matter."

Trump has until Friday to contest the request.

Also read: Trump on trial

The Justice Department motion to unseal the warrant noted — and did not dispute — statements by Trump's representatives that the FBI was seeking presidential records and potential classified material.

According to US media, the search related to potential mishandling of classified documents taken to Mar-a-Lago after Trump left the White House in January 2021.

Political firestorm

The FBI raid on Trump's palatial Mar-a-Lago residence has sparked a political firestorm in an already bitterly divided country and comes as he is weighing another White House run in 2024.

Trump has condemned Monday's raid as politically motivated and a "weaponisation" of the Justice Department.

"Nothing like this has ever happened to a president of the United States before," he said.

In a statement on his Truth Social platform on Thursday, Trump said his attorneys had been "cooperating fully" and "the government could have had whatever they wanted, if we had it."

"And then, out of nowhere and with no warning, Mar-a-Lago was raided at 6:30 in the morning," he said, adding that agents even "went through the first lady's closets and rummaged through her clothing and personal items."

Garland criticised "unfounded attacks on the professionalism of the FBI and Justice Department agents and prosecutors" following the raid.

"I will not stand by silently when their integrity is unfairly attacked," he said.

"Men and women of the FBI and the Justice Department are dedicated patriotic public servants."

Leading Republicans have rallied around the former president and harshly denounced the Justice Department and FBI.

'Without fear or favor'

US police were engaged in a standoff on Thursday with an armed man who tried to break into an FBI office in Cincinnati, Ohio, although there was no immediate indication the event was linked to the raid on Trump's home.

The Justice Department typically does not confirm or deny whether it is investigating someone.

Garland, a former prosecutor and judge who has a reputation as a stickler for protocol, took pains to emphasise the law was being applied fairly.

"Faithful adherence to the rule of law is the bedrock principle of the Justice Department and of our democracy," he said. "Holding the rule of law means applying the law evenly without fear or favor."

Since leaving office, Trump has remained the country's most divisive figure and a force in the Republican party, continuing to sow falsehoods that he actually won the 2020 vote.

On Wednesday, the 76-year-old Trump was questioned for four hours by Letitia James, the New York state attorney general who is investigating the business practices of the Trump Organization.

Trump is also facing legal scrutiny for his efforts to overturn the results of the 2020 election and over the January 6 attack on the US Capitol by his supporters.

Trump was impeached for a historic second time by the House after the Capitol riot — he was charged with inciting an insurrection — but was acquitted by the Senate.