WASHINGTON  — Former national security adviser Michael Flynn is to plead guilty Friday to making false statements to the FBI, becoming the fourth person charged in a wide-ranging investigation led by special counsel Robert Mueller and his team of prosecutors.

Court documents show Flynn, an early and vocal supporter on the campaign trail of President Donald Trump, will admit to lying to the FBI about his conversations during the transition period with Russia's ambassador to the United States.

Flynn, who was interviewed by the FBI just days after Trump's inauguration, was forced to resign in February after White House officials said he had misled them about whether he had discussed sanctions with the ambassador, Sergey Kislyak.

A plea hearing is scheduled for 10:30 A.M. EST before U.S. District Judge Rudolph Contreras.

Flynn's lawyer, Robert Kelner, did not immediately return messages seeking comment.

Mueller's team announced charges last month against three other Trump campaign officials, former chairman Paul Manafort and his business associate Rick Gates, and a former foreign policy adviser, George Papadopoulos.

Signs of Flynn cooperating with Mueller's team surfaced in the past week, as his lawyers told the legal team they could no longer discuss information about the case with them. Scheduled grand jury testimony regarding Flynn was also postponed.

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