The warrant says the vessel, all the oil aboard and $995,000 are subject to forfeiture.

The US Justice Department unveiled a warrant Friday for the seizure of the Iranian oil supertanker Grace 1, one day after a Gibraltar judge allowed the release of the detained vessel.

The United States called for the seizure of the ship, which was still anchored in the British Mediterranean territory on Friday, for "a scheme to unlawfully access the US financial system to support illicit shipments to Syria from Iran by the Islamic Revolutionary Guard Corps (IRGC), a designated foreign terrorist organization," the Justice department said.

The warrant says the vessel, all the oil aboard and $995,000 are subject to forfeiture based on violations of the International Emergency Economic Powers Act (IEEPA), and bank fraud, money laundering, and terrorism forfeiture statutes.

Earlier Friday Iranian officials said the tanker was preparing to set sail after a Gibraltar judge ordered its release, six weeks after it was detained in apparent retaliation for Iran's seizure of a British-flagged tanker in the Gulf.

The Grace 1 was to be renamed and switch to the Iranian flag for its onward journey, the deputy head of Iran's Ports and Maritime Organisation, Jalil Eslami, told Iranian state television Friday.

But according to an AFP source, the ship was awaiting the arrival of a new crew before it would leave Gibraltar.