The White House has confirmed it asked an FBI official to discredit reports President Trump's campaign aides were in touch with Russian intelligence.
The White House acknowledged its chief of staff Reince Priebus asked the FBI's deputy director to dispute a New York Times article alleging Moscow links.
CNN reports the FBI refused, citing an ongoing inquiry into claims of contacts between Trump aides and Russia.
Mr Trump has responded on Twitter by railing against FBI "leakers".
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"The FBI is totally unable to stop the national security 'leakers' that have permeated our government for a long time," Mr Trump, who is due to address a conservative political gala on Friday morning, tweeted.
"They can't even find the leakers within the FBI itself. Classified information is being given to media that could have a devastating effect on US. FIND NOW."
The New York Times reported last week that US agencies intercepted phone calls last year between members of Mr Trump's presidential campaign and Russian intelligence agents.
Mr Priebus asked FBI deputy director Andrew McCabe to pour cold water on suggestions of communications between Mr Trump's staff and Moscow.
As of Friday, the FBI has not commented publicly on the report.
White House press secretary Sean Spicer refuted the CNN report.
"We didn't try to knock the story down. We asked them to tell the truth," he said.
Mr Trump has been dogged by claims of alleged links to Moscow since his presidential campaign.
The president asked for national security adviser Michael Flynn's resignation last week after he misled Vice-President Mike Pence about his contacts with a Russian ambassador during the transition.Image copyright AP Image caption Mr Flynn dines with Russian leader Vladimir Putin in December 2015
When pressed about Moscow ties last week, Mr Trump said "nobody that I know of" spoke with Russian intelligence officials during the campaign.
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Democrats said Mr Priebus was in violation of a policy limiting communication between the White House and law enforcement on pending investigations.
Michigan Representative John Conyers, a member of the House Judiciary Committee, said: "The White House is simply not permitted to pressure the FBI to make public statements about a pending investigation of the president and his advisers."