The legal team for Alexander Vinnik, a Russian national recently extradited to the United States for his alleged role at defunct crypto exchange BTC-e, has reportedly been urging officials to consider a prisoner swap.

According to a Monday report from Reuters, a lawyer representing Vinnik called on Russian foreign minister Sergey Lavrov to conduct negotiations with U.S. officials to bring the accused Bitcoin (BTC) launderer back to his home country. Russian authorities currently have several U.S. citizens in custody under questionable charges, including basketball star Brittney Griner, educator Marc Hilliard Fogel and Paul Whelan, a former Marine detained for allegedly committing espionage.

"The only thing that can save Alexander is for the Russian Federation to enter into negotiations with the American authorities within the framework of the exchange of prisoners between the countries mentioned," a letter from Vinnik’s lawyer, Frederic Belot, reportedly noted.

Vinnik allegedly helped launder roughly $4 billion worth of Bitcoin through his role at BTC-e, one of the world’s largest crypto exchanges at the time, with some of the funds possibly coming from the hack of Japan-based crypto exchange Mt. Gox. Authorities in Greece arrested Vinnik in July 2017, at which point, the governments of France, Russia and the U.S. fought for extradition.

The U.S. Justice Department reported that Vinnik had been extradited on Aug. 4 from Greece to the United States to face charges related to having an unlicensed money service business, conspiracy to commit money laundering, money laundering and engaging in unlawful monetary transactions. According to authorities, BTC-e “facilitated transactions for cybercriminals worldwide and received