(Washington) An American nuclear submarine is in Cuba, the Pentagon announced Thursday the day after the arrival of a Russian nuclear-powered submarine on the communist island.

“The nuclear attack submarine USS Helena is in Guantanamo Bay as part of a routine visit,” the US Southern Command said on social media, referring to the US naval base. on the island of Cuba.

This visit and its schedule were “planned”, according to the same source.

The day before, the nuclear-powered submarine “Kazan” entered Havana Bay along with three other Russian ships. None of them carry nuclear weapons, according to Cuban authorities.

The unusual Russian deployment, some 150 miles from the coast of Florida, comes at a time of high tensions between Washington and Moscow over the war in Ukraine, where the U.S.-backed government is fighting a Russian invasion.  

The United States said it was monitoring developments in Cuba, but said the deployment of Russian ships did not pose a direct threat.  

During the Cold War, Cuba was the ally of the USSR. The discovery of Soviet missiles in Cuba in 1962 triggered a serious crisis that nearly degenerated into war between the United States and the Soviet Union.