US President Donald Trump has attacked the integrity of the FBI and Justice Department in an extraordinary showdown over the expected White House release of a secret Republican memo alleging FBI bias against him in its Russia probe.
Mr Trump, who has long been angered over the probe, accused the country's top law enforcement officers, some of whom he appointed himself, of politicising investigations in favour of Democrats and against his fellow Republicans.
Mr Trump has repeatedly complained about his treatment by federal investigators probing possible collusion between his campaign and Russia to sway the 2016 presidential election, and any actions to impede the investigation.
"The top leadership and investigators of the FBI and the Justice Department have politicised the sacred investigative process in favour of Democrats and against Republicans - something which would have been unthinkable just a short time ago," Mr Trump said on Twitter. The president praised "rank and file" FBI employees.
The timing of his latest salvo, two days after the FBI warned publicly against releasing the classified memo, was sure to worsen the president's frayed relations with agencies that are supposed to be politically independent.
Representatives for the Federal Bureau of Investigation and the Justice Department could not be immediately reached for comment.
A White House official said Mr Trump was likely to give congress approval on Friday to release the four-page document that has become a flashpoint in a wider battle between Republicans and Democrats over Special Counsel Robert Mueller's Russia probe.
The criminal probe grew out of the FBI's Russia investigation after Mr Trump fired FBI director James Comey and Attorney General Jeff Sessions recused himself from the investigation.
Russia has denied meddling in the election campaign. Mr Trump, who has called Mueller's probe a political witch hunt, has denied any collusion or obstruction of justice.
The FBI expressed "grave concerns about material omissions of fact" in the Republican memo on Wednesday, in a rare public rebuke of the president and Republicans in congress pushing to release the memo.
Democrats have depicted the memo, which was crafted by Republican members of the House Intelligence Committee, as misleading, based on a selective use of highly classified data and intended to discredit Mueller's work.
There has been speculation that FBI director Christopher Wray, appointed by Mr Trump after he fired Comey, might resign if Mr Trump allows release of the memo.
The memo, commissioned by Republican Devin Nunes, chairman of the House Intelligence Committee, purports to show that the FBI and Justice Department misled a US court in seeking to extend electronic surveillance of Trump campaign adviser Carter Page, multiple sources familiar with it have said.