Russia’s ambassador has called on American authorities to release convicted arms merchant Viktor Bout from his Illinois federal prison, citing fears that he might contract coronavirus.

Anatoly Antonov, Russia’s ambassador in Washington, mentioned Bout among several Russians imprisoned in U.S. facilities in the latest in an extended series of diplomatic moves aimed at repatriating convicts who have become international causes for Russian President Vladimir Putin’s regime.

Bout is serving a 25-year sentence at the federal medium-security prison at Marion, Ill. He was convicted in November 2011 on four conspiracy counts stemming from a U.S. Drug Enforcement Agency sting operation.

Bout told U.S. informants disguised as South American terrorist operatives that he could provide them with millions of dollars in anti-aircraft missiles and other weapons. Bout was transferred to the prison after being sentenced in 2012. His 2008 arrest in Bangkok by U.S. Drug Enforcement Administration agents and Thai police followed more than a decade of his exploits in Africa, Asia and the Mideast and a frenetic international effort to apprehend him, a saga chronicled in the book, “Merchant of Death.”

Antonov cited “the difficult COVID-19 situation in the United States” in urging American authorities to “pay attention to Russian citizens kept in U.S. jails,” according to the Russian news agency Tass. “It’s time for resolute action,” Antonov said.

The diplomatic broadside about virus fears is the latest official Russian diplomatic effort to free Bout after his repeated legal efforts to overturn his conviction were spurned by the U.S. Supreme Court. In September 2019, Russian embassy officials asked the U.S. to send Bout back to Moscow in exchange for as many as 15 American residents now jailed in Russia. Bout’s wife, Alla, described that effort at the Russian consulate in New York that month, saying that the Russian government request for a prisoner swap for Bout had been turned down by the U.S.

“The Russian government has made attempts at exchange. They offered 14 or 15 people,” Alla Bout was quoted in Tass at the time. Bout’s wife said that the Russian offers were “of little interest” to U.S. officials and that the U.S. was intent on Bout serving “his sentence as a warning to others.”