The US House Intelligence Committee's top Democrat has accused Republicans of amending a memo about claims of FBI surveillance at the 2016 election.
Adam Schiff said Republicans had changed the text after it was voted on.
The secret document was passed by the Republican-dominated committee but needs approval from President Donald Trump to be made public.
It is believed to accuse the FBI of abusing its surveillance powers to target the Trump campaign.
The four-page document was compiled by staffers for House Intelligence Committee head Devin Nunes, a member of Mr Trump's Republican party.
Concerns about its contents were raised by the FBI itself which complained of "material omissions of fact that fundamentally impact the memo's accuracy".
Democrats fear the document may be an attempt to discredit the inquiry into Trump campaign links to Russia, which is being led by Special Counsel Robert Mueller.
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