A former campaign aide to Donald Trump has pleaded guilty to lying to federal agents working for special counsel Robert Mueller as part of his probe into possible co-ordination between the Trump campaign and Russia.
George Papadopoulos pleaded guilty to one count of lying to FBI agents about the nature of his interactions with "foreign nationals" who he thought had close connections to senior Russian government officials.
He pleaded guilty on October 5, and the plea was unsealed on Monday.
He is the first person to face criminal charges that cite interactions between Trump campaign associates and Russian intermediaries during the 2016 presidential campaign.
Papadopoulos was a member of the campaign's foreign policy team, but Trump aides have said he played a limited role in the campaign and had no access to the candidate.
Court papers revealed that Papadopoulos was told about the Russians possessing "dirt" on Democrat Hillary Clinton in the form of "thousands of emails" on April 26 2016, well before it became public that the Democratic National Committee and Clinton campaign chairman John Podesta's emails had been hacked.
Papadopoulos has been co-operating with investigators, according to court papers, a potentially ominous sign for others in the Trump orbit who might be implicated by his statements.
The White House declined to comment on the details of the Papadopoulos plea, and Mr Trump's Twitter account was also silent on the plea.
The interactions at the centre of the case included speaking with Russian intermediaries who were attempting to line up a meeting between Mr Trump and Russian President Vladimir Putin and offering "dirt" on Mrs Clinton.
The court filings do not provide details on the emails or whom Papadopoulos may have told about the Russian government effort.
The FBI interviewed Papadopoulos about his Russian connections on January 27, a week after Mr Trump's inauguration. The interview predates Mr Mueller's appointment but was part of the FBI probe into Russian election interference that he has taken over.
Papadopoulos was arrested over the summer at Dulles International Airport and has since met government officials "on numerous occasions to provide information and answer questions".