A Russian court sentenced U.S. Marine veteran Robert Gilman to 4.5 years in a penal colony Tuesday, roughly a week after his conviction on charges of assaulting a police officer.

Gilman was first arrested in January on a train from Sochi to Moscow after passengers complained about his belligerence. Gilman, who was drunk at the time, bruised a Russian police officer with a kick while being dragged off of the train. Gilman is one of several U.S. citizens currently serving years-long sentences in Russian prisons.

The U.S. State Department did not respond to a request for comment on Gilman's case from Fox News Digital.

"This is another case that demonstrates that Americans are not safe in Russia, especially Americans of Russian descent and especially now when the relations between Moscow and Washington are at the lowest point in history, including the Cold War," Rebekah Koffler, a strategic intelligence expert and author of "Putin’s Playbook" told Fox.

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Russia Putin

Russia President Vladimir Putin. (Alexander Demyanchuk, Sputnik, Kremlin Pool Photo via AP)

Gilman is an American of Russian descent whose parents both attended Moscow State University. He speaks fluent Russian and appealed to the Russian court for a lower sentence in a bilingual speech, Koffler added.

"The Russian authorities prey on people like that. They are looking for Russian-Americans to return to mother Russia and to serve as propaganda props, who would badmouth America and praise Russia. The Russians will likely intimidate him into cooperating with them for some anti-American activities," she continued.

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Gilman's sentencing comes weeks after the U.S. and Ukraine exchanged prisoners with Russia, securing the release of hundreds of Ukrainian prisoners of war and two Americans, among other nationals.

Russia is currently holding several American citizens in its prisons, the most high-profile of whom is Brittney Griner. Griner is a WNBA star who was sentenced to 9 years in prison for marijuana possession earlier this year.

Brittney Griner behind bars

A Russian court found Brittney Griner guilty of smuggling and storing narcotics after prosecutors requested a sentence of nine and a half years in jail for the athlete. (EVGENIA NOVOZHENINA/POOL/AFP via Getty Images)

U.S. Marine Veteran Paul Whelan is also serving a 16-year prison sentence in the country on espionage charges.

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The U.S. and Russia have engaged in talks for a prisoner swap, but no progress has been announced.