WASHINGTON President Donald Trumps former national security adviser pleaded guilty Friday morning to lying to the FBI about his contacts with the Russian government, an extraordinary development in special counsel Robert Muellers investigation into Russian interference in the 2016 election.

Michael Flynn was charged with one count of making a false statement to FBI agents and appeared in federal court in D.C.

In a criminal information filing from Muellers team, the government alleges that Flynn willfully and knowingly made materially false, fictitious, and fraudulent statements in an interview with FBI agents on Jan. 24. It alleges he falsely told the FBI that he did not ask the Russian ambassador to refrain from retaliating to sanctions the Obama administration imposed on Russia in late December. Flynn also allegedly lied about asking the Russian ambassador on Dec. 22 to delay or defeat a pending United Nations Security Council resolution.

Considering all of the additional charges Flynn could have faced in connection with his overseas dealings, the fact that he is facing only one charge is an indication that Flynn is offering significant cooperation and information that could further Muellers investigation.