An American Marine Corps veteran detained in Russia since 2022 is now hospitalized in serious condition, according to an advocate for his family, who is urging the Trump administration to push for his immediate release on humanitarian grounds.

Robert Gilman, 32, is being held at a Russian hospital in what his advocate, Eric Lebson of Global Reach, described as a "dissociative stupor," adding Gilman is being fed through a tube in his nose.

Lebson alleged that Russian authorities have subjected Gilman to mistreatment, including harassment, forced exercise sessions lasting up to 16 hours and the administration of psychotropic drugs. Lebson also alleged Gilman was pressured to fight in Ukraine.

CBS News has not independently verified those claims, and Russian officials have not publicly responded.

"The situation with Robert is far beyond anything we have seen with any other American detained in Russia," Lebson said. "It concerns us that it could end similar to what happened to Otto Warmbier in North Korea. It is urgent that the Russians release Robert now so the U.S. can get him the emergency medical care he needs."

The State Department did not immediately reply to a request for comment on Gilman's case.

Reuters was first to report on Gilman's status.

Gilman's case comes as the Trump administration weighs whether to try to restart negotiations with Moscow over the war in Ukraine. Those efforts have slowed in recent weeks as the administration has focused on the escalating conflict with Iran and broader Middle East tensions.

The Trump administration previously secured the release of several Americans held by Russia, including teacher and Ksenia Karelina, a U.S.-Russian dual citizen who was freed as part of a prisoner exchange. But as many as 10 Americans are believed to be detained in Russia, according to sources familiar with their cases.

Other high-profile Americans released from Russian custody in previous years include former Marine Paul Whelan, Wall Street Journal reporter Evan Gershkovich and WNBA star Brittney Griner.