American Paul Whelan has again asked President Joe Biden to do everything in his power to secure his release, along with the release of other Americans who are imprisoned in Russia.

Whelan is serving a 16-year sentence in a Russian prison on espionage charges which both he and the U.S. Department of State deny are legitimate. He is a former U.S. Marine who has been imprisoned in Russia since 2018 and has faced years of fighting for his release, working in a remote labor camp and even being assaulted while incarcerated.

Last year Whelan was assaulted by a fellow inmate, saying he was struck in the face "with a closed fist" by a Turkish prisoner who held anti-American views, according to a clip obtained at the time by outlets including CNN.

Whelan was arrested in 2018 in a hotel in Moscow, and the U.S. has listed him as "wrongfully detained."

Whelan's family has advocated for his release as they watched him get passed up in various prisoner swaps that included the high-profile deal made to bring WNBA star Brittney Griner home last December, swapping her for notorious Russian arms dealer Viktor Bout.