The Iran-flagged supertanker that left port in Gibraltar has reportedly been leased out to the country's Revolutionary Guard, in an apparent show of defiance to the U.S., which tried to seize the vessel because of its ties to the elite group designated by the Trump administration a terror organization.

TANKER FILLED WITH OIL HEADED TO SYRIA: SOURCE

The tanker, Adrian Darya 1, previously named Grace 1, is believed to be hauling $130 million in light crude oil. It lifted anchor in Gibraltar late Sunday and its location has been monitored. As of early Wednesday, MarineTraffic.com showed the tanker in international waters off the Iberian Peninsula. Iran appeared confident that the ship -- despite U.S. efforts to stop its voyage -- is not in danger.

“The Adrian Darya vessel needs no escort,” Alireza Tangsiri, head of the Revolutionary Guard's navy, told the Iranian Labour News Agency, according to Reuters.

Tangsiri said the ship is "Korean-made" and owned by Russia. The U.S. argued in unsealed court documents that Iran's Islamic Revolutionary Guard Corps is the ship's true owners through a network of front companies.

Authorities in Gibraltar said Sunday that, unlike in the U.S., Iran's Revolutionary Guard is not designated a terror organization under EU, U.K. or Gibraltar law.

The vessel had been detained for a month in the British overseas territory for allegedly attempting to breach European Union sanctions on Syria. The Iranian ship was detained while sailing under a Panamanian flag with the name Grace 1. It changed the name on Sunday and hoisted an Iranian flag.

Gibraltar authorities rejected a last-minute attempt by the U.S. to reseize the tanker, arguing that EU regulations are less strict than U.S. sanctions on Iran.

The chief minister of Gibraltar, Fabian Picardo, said he had been assured in writing by the Iranian government that the tanker wouldn't unload its cargo in Syria.

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Secretary of State Mike Pompeo warned Iran about any shipments to Syria in the face of U.S. sanctions, Reuters reported.

The Associated Press contributed to this report.