Up to 5,000 Cubans have joined Russian forces in Ukraine, according to a U.S. assessment cited in a Reuters report.

An unclassified State Department cable dated October 2, obtained by Reuters, instructs American diplomats to urge foreign governments to vote against a United Nations resolution calling for an end to the U.S. embargo on Cuba, citing Havana’s alleged support for Moscow’s war effort. The non-binding resolution has been adopted by wide margins in the U.N. General Assembly every year since 1992.

The cable states that “after North Korea, Cuba is the largest contributor of foreign troops to Russia’s aggression,” estimating between 1,000 and 5,000 Cubans are fighting in Ukraine.

A State Department spokesperson said Washington is aware of reports that Cubans are serving alongside Russian forces and accused the Cuban government of failing to prevent its citizens from being recruited for the war. 

He added that Cuba was using the annual U.N. resolution to portray itself as a victim and that it did not deserve support from America’s democratic allies.

“The Trump Administration will not remain on the sidelines or support an illegitimate regime that undermines our national security interests in our region,” the spokesperson told Reuters. 

Cuba has not publicly addressed the allegations. 

Since returning to office in 2025, Trump has strengthened sanctions on Cuba, reinstated its designation as a state sponsor of terrorism, and imposed penalties on foreign nationals doing business with Cuban state entities.

Cuba and Russia have maintained close ties since the Cold War. In 2024, Cuba joined the Russian-led BRICS group as a partner country.

Since launching its full-scale invasion in 2022, Moscow has recruited foreign fighters from countries including Nepal, Somalia, India, and North Korea.