WASHINGTON — George Papadopoulos, a former campaign adviser to President Donald Trump, pleaded guilty earlier this month to lying to federal officials about his contacts with Russian nationals he believed had ties to the Russian government during Trump’s presidential campaign.

Papadopoulos, who was named by Trump in March 2016 as a foreign policy adviser to the campaign, pleaded guilty to lying about his contacts with the Russians when he was interviewed in January by federal agents who were investigating Russian interference in the presidential campaign.

Papadopoulos told agents that he had been in contact with a Russian professor even prior to joining the campaign. In fact, prosecutors say he met the man in March 2016 and was told by the professor the next month that he had damaging information about Democratic presidential candidate Hillary Clinton, including thousands of Clinton’s emails.

Papadopoulos also falsely told agents he believed the professor was a low-level person in Russia, but, in fact, he knew that the professor had ties to senior levels of the Russian government, according to court papers released Monday.

Neither Papadopoulos nor a representative could be reached immediately Monday for comment.

Papadopoulos’s plea indicates he is cooperating with Special Counsel Robert Mueller .

The charge indicates that Mueller, who is known to be probing alleged coordination between the Trump campaign and the Kremlin, is deeply probing contacts with Trump campaign aides and Russian officials.

The court papers show that Papadopoulos had also met a Russian woman he believed had ties to the Kremlin and with whom he communicated about setting up a meeting between Trump campaign officials and Russian officials.

He told agents that he met the woman a year before joining the Trump campaign, but, in fact, he met her only after he was named to the campaign and communicated with her for months while working with Trump aides, the documents show.

Papadopoulos’s plea agreement shows he was introduced to the woman by the professor, and she claimed she was a relative of Russian President Vladimir Putin. According to the plea, she told Papadopoulos she would like to help set up meetings for the Trump campaign with her associates to discuss U.S.-Russia ties under a future President Trump.

Papadopoulos emailed campaign officials about her offer. A supervisor, who is not named, wrote back, “Great work.”

The Washington Post has reported that Papadopoulos repeatedly emailed top campaign aides to set up such meetings, and some emails show his offers were rebuffed.

Prosecutors allege he obstructed their inquiry by deleting a Facebook page that would have revealed his contacts with Russians not long after learning of the investigation.