A LAST-MINUTE U.S. warrant to seize an Iranian oil tanker preparing to leave Gibraltar after weeks of detention cast doubt over its departure Saturday, prolonging a diplomatic spat between Tehran, London and Washington.

The U.S. Justice Department alleged the ship was part of a scheme “to unlawfully access the U.S. financial system to support illicit shipments to Syria from Iran by the Islamic Revolutionary Guard Corps,” which Washington has designated a foreign terrorist organization.

There was no comment from Britain or Gibraltar, its overseas territory.

Any detention order would ultimately have to come from Gibraltar’s Supreme Court. So far, that has not happened and the ship is still free to sail.

Richard de la Rosa, managing director of Astralship, the vessel’s shipping agent, said the ship was preparing for departure.

“Within the next two days, she’ll be going,” he said.

“They’re performing crew changes. She needs some reprovisioning,” he said, adding that new Indian and Ukrainian crew members were due to arrive the next day.

Gibraltar seized the ship July 4 on suspicion it was transporting oil to Syria in breach of European Union sanctions, triggering a sharp deterioration in relations between Tehran and London. Iran has repeatedly denied this.

Iran subsequently detained the British-flagged tanker Stena Impero in what was seen as a tit-for-tat move.

On Thursday, Gibraltar’s Supreme Court ordered the tanker released after the British overseas territory said it had received assurances from Iran that the Grace 1 would not head to any country subject to EU sanctions.

But in a last-minute twist Friday, the United States, which is at loggerheads with Iran, issued the warrant.

It says the vessel and all the oil aboard are subject to forfeiture based on violations of U.S. sanctions.

It also cites violations of bank fraud, money laundering and terrorism statutes.

The U.S. State Department has also threatened to issue a visa ban on anyone working on the ship. (SD-Agencies)