A secret Republican Party memo claiming FBI bias against President Donald Trump could be released on Friday, despite a warning being issued by the law enforcement agency.
The White House has been working to clear the release of the four-page document put together by Republican members of the House of Representatives Intelligence Committee.
It reportedly accuses the Department of Justice (DoJ) and the FBI of abusing a surveillance programme.
The programme is notably connected to a warrant issued to spy on Trump campaign aide Carter Page. The warrant was allegedly issued based on unproven claims against the US leader based on the Trump-Russia dossier – opposition research paid for by Democrats.
The document's impending release has sparked fears it could threaten national security.
It is currently subject to a review by White House national security experts.
The memo row comes amid a wider battle between Republicans and Democrats over Special Counsel Robert Mueller's investigation into alleged collusion between Mr Trump's presidential campaign and Russia to help him secure a victory.
The probe also looks into whether the US leader tried to obstruct the investigation.
Both Russia and the now-President have both denied any collusion.
Sky News US Correspondent Cordelia Lynch said: "Trump campaign officials now believe that this is evidence that Donald Trump was treated unfairly – but the Democrats believe this is an attempt to discredit the Robert Mueller investigation."
She added: "There is a lot of concern and it now means that Donald Trump and the FBI are on this collision course and it is already proving explosive."
Democrats have hit out at the decision to release the memo, which the the White House confirmed Mr Trump had read, claiming it is intended to undermine the investigation.
They said it was misleading and based on a selective use of highly-classified information intended to tarnish Mr Mueller's probe.
House of Representatives Speaker Paul Ryan said the memo on FBI surveillance was not an indictment of the FBI or the Justice Department but a legitimate bid to ensure the law enforcement agency carried out surveillance correctly.
"If American civil liberties were abused, then that needs to come to light so that that doesn't happen again," he said.
"This memo is not an indictment of the FBI, of the Department of Justice."
Senior Republican senator John Thune had urged colleagues to allow the Senate Intelligence Committee to review the document and listen to the FBI's concerns before making it public.
Democrats on the committee produced their own memo, which Republicans on the panel stopped from being released at the same time. Mr Thune denounced the move.
The release of the memo could prompt high-level resignations within the United States' law enforcement agencies.
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"The FBI was provided a limited opportunity to review this memo the day before the committee voted to release it," an FBI spokesperson said.
"As expressed during our initial review, we have grave concerns about material omissions of fact that fundamentally impact the memo's accuracy."