A former top FBI official is facing criminal charges for allegedly trying to help a Russian oligarch get off a US sanctions list, prosecutors say.
Charles McGonigal was arrested alongside an ex-Russian diplomat on Saturday. The pair face money laundering and conspiracy charges.
Mr McGonigal also faces charges he took $225,000 (£181,612) in cash from a foreign agent while still in the FBI.
He is one of the highest-ranking FBI agents to ever be charged with a crime.
Mr McGonigal was arrested on Saturday after returning to JFK International Airport in New York from international travel, and on Monday entered a plea of not guilty at a federal courthouse in Manhattan.
According to federal prosecutors, the 54-year-old Mr McGonigal - who was in charge of FBI counterintelligence in New York before his retirement in 2018 - and former Russian diplomat Sergey Shestakov violated US sanctions by agreeing to provide services to Russian billionaire and industrialist Oleg Deripaska.
Mr Deripaska, 55, is reportedly once Russia's richest man and was president of energy company En+ Group and United Company Rusal - the world's second largest aluminium company - before leaving both firms in 2018. He was hit with sanctions the same year, with the US accusing him and a handful of other Russian oligarchs and officials of "malign activity around the globe".
US Attorney Damian Williams said in a statement on Monday that Mr McGonigal and Mr Shestakov "both previously worked with Deripaska to attempt to have his sanctions removed".
"As public servants, they should have known better."
Prosecutors believe the two men agreed to investigate a rival oligarch and have Mr Deripaska removed from a list of individuals sanctioned by the US.
The men and an associate of Mr Deripaska are accusing of "using shell companies as counterparties in the contract that outlined the services to be performed, using a forged signature on that contract, and using the same shell companies to send and receive payments from Deripaska", prosecutors allege.
Mr McGonigal faces separate charges that he took cash while still serving in the FBI "from an individual who had business interests in Europe and who had been an employee of a foreign intelligence service".
Prosecutors did not name the individual but describe the person as a former "foreign security officer and businessperson" with interests abroad.
Mr McGonigal and Mr Shestakovnow face four sanctions-related and money laundering charges, each of which carry possible sentences of up to 20 years in prison. Mr Shestakov also faces charges that he made false statements, punishable by another five years.
In the separate charges, Mr McGonigal faces six counts of false statements - each punishable by five years - as well as two counts of falsification of records and documents, each of which carries a maximum penalty of 20 years.