Washington DC - US Attorney General Merrick Garland on Thursday rejected accusations that the Justice Department has been "weaponized" against Republicans and condemned increasingly "dangerous" threats to its employees.

"Our norms are a promise that we will not allow this department to be used as a political weapon," Garland said in an unusually forceful speech to the workforce of the Justice Department.

"And our norms are a promise that we will not allow this nation to become a country where law enforcement is treated as an apparatus of politics," he said.

Garland (71) did not mention Donald Trump by name, but the former president and current Republican White House candidate frequently accuses the Justice Department of waging a "political witch hunt" against him.

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Garland defended the integrity of the department and said its guiding principle was to "follow the facts and apply the law" with fairness and impartiality.

"There is not one rule for friends and another for foes, one rule for the powerful and another for the powerless, one rule for the rich and another for the poor, one rule for Democrats and another for Republicans," the attorney general said.

Trump faces charges in Washington brought by a special counsel of conspiring to overturn the results of the 2020 election he lost to Democrat Joe Biden. He faces similar state charges in Georgia.

He was convicted in New York in May of falsifying business records and indicted in Florida on federal charges of mishandling classified documents after leaving the White House.

The Florida charges were dismissed by a judge appointed by Trump on the grounds that the special counsel was unlawfully appointed by Garland.

Garland praised the tens of thousands of Justice Department employees for "bravely" doing their duty "in the face of an unprecedented spike in threats targeting a range of public officials across the country."

"These attacks have come in the form of conspiracy theories, dangerous falsehoods, efforts to bully and intimidate career public servants by repeatedly and publicly singling them out, and threats of actual violence," he said.

"Through your continued work, you have made clear that the Justice Department will not be intimidated by these attacks," Garland said. "But it is dangerous – and outrageous – that you have to endure them."