Washington DC - The US Coast Guard said Friday it had intercepted a ship transporting oil to Cuba in violation of a oil blockade imposed in January.

"In early September, a Coast Guard tactical team boarded M/V Grace in the Caribbean Sea" as it was "transiting to Cuba, carrying fuel," a Coast Guard statement said.

The vessel "was believed to be employing tactics common amongst the 'dark fleet,'" the statement said.

The term describes ships that transport sanctioned or high-risk commodities while concealing their origin, ownership, and destination, per the International Maritime Rescue Federation.

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The Grace was then escorted to the port of Progreso, in eastern Mexico, where the Mexican navy "confirmed the presence of large quantities of fuel in the vessel's ballast tanks," the Coast Guard statement said.

Earlier this summer, the Coast Guard boarded and detained the Jaira Provider, "another substandard vessel determined to be carrying illicit fuel to Cuba," it said.

Relations between Washington and Havana have worsened since President Donald Trump returned to power in January 2025.

The Republican leader says the Communist island located just 150 kilometers (90 miles) from Florida represents an extraordinary threat to the US.

Since January, Washington has imposed a de facto oil embargo on the island of 9.4 million people, plunging the country into a deep economic and energy crisis.