Russian warships enter Havana harbor under Washington's watchful eye 100 miles (160 km) to the U.S.

Havana is just 100 miles (160 km) from Key West, Florida, home to a U.S. Naval Air Station. The timing of the visit - as the Biden administration ponders how far to go in helping defend Ukraine against Russia - suggests more than "standard practice," said William Leogrande, a professor at American University.

"The visiting Russian warships are Putin's way of reminding Biden that Moscow can challenge Washington in its own sphere of influence," Leogrande said.

The stopover coincides with Cuba's worst social and economic crisis in decades, with shortages of everything from food, medicine and fuel and growing discontent on the streets.