Washington DC - US forces boarded a third tanker ship in the Indian Ocean that had violated President Donald Trump's blockade of sanctioned vessels in the Caribbean and fled the region, the Pentagon said Tuesday.

"From the Caribbean to the Indian Ocean, we tracked it and stopped it," the Pentagon said in a post on X that included a video clip of US forces roping down from helicopters onto the tanker Bertha.

"The vessel was operating in defiance of President Trump's established quarantine of sanctioned vessels in the Caribbean and attempted to evade," the Pentagon said of the overnight operation.

The Defense Department "will deny illicit actors and their proxies freedom of maneuver in the maritime domain," it added.

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It is the third ship that US forces have intercepted in the Indian Ocean this month, and the 10th overall since Trump ordered a "blockade" of sanctioned oil vessels heading to and from Venezuela in December.

But those ships seized in recent months make up only a tiny fraction of the total number of sanctioned "shadow fleet" vessels operating worldwide to evade sanctions, which a senior US Coast Guard officer said number up to 800.