The ship has reportedly been subject to US sanctions before and most recently docked in Venezuela, a US government source told Bloomberg.
Most of Venezuelan oil goes to China, usually through intermediaries, at steep discounts due to the sanctions.
The U.S. seizure of a Venezuelan tanker is a clear escalation from financial sanctions to physical bans. It raises the stakes for Caracas and all those who facilitate its exports, Jorge Leon, head of geopolitical analysis at research firm Rystad Energy, told Bloomberg.
Venezuelan President Nicolás Maduro demanded late Wednesday evening that Washington cease its interventions against the Latin American country.
"From Venezuela, we ask and demand an end to the illegal and brutal intervention by the US government against Venezuela and Latin America," he told supporters in the capital, AFP writes.
The United States has in recent months carried out attacks on ships allegedly transporting drugs off the coast of Venezuela. Trump has blamed Venezuela's Maduro for the attacks. Several American warships are also in the waters of the Caribbean Sea near Venezuela.
