The oil tanker Grace 1 is seen July 4 after it was seized by Gibraltar authorities and British Royal Marines. File Photo by A. Carrasco/EPA-EFE

Aug. 15 (UPI) -- Officials in Gibraltar on Thursday released a captive oil tanker that was seized by British authorities last month -- over objections from the United States, which lobbied to block the vessel from returning to Iranian control.

Gibraltar officials released the Grace 1 tanker on the condition it not transport 2.1 million barrels of crude oil on board to Syria -- a move that would violate European Union sanctions. The Gibraltar high court said it received a written assurance from Tehran it would avoid Syria.


Following the Grace 1 tanker's release, the U.S. Department of State said that since it was assisting the Islamic Revolutionary Guard Corps, its crew will be made ineligible for visas or admission to the United States under terrorism-related inadmissibility grounds.

"The maritime community should be aware that the U.S. government intends to revoke visas held by members of such crews," Department spokeswoman Morgan Ortagus said in a statement. "In the case of the M/T Grace 1, we will continue to act consistent with our existing policies concerning those who provide material support to the IRGC."

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She said it would use all tools at its disposal to deny Iran with resources needed to destabilize activities in Syria.

The U.S. Justice Department appealed earlier Thursday to take the vessel. At a hearing, the Gibraltar government told the court about the request. Chief Justice Anthony Dudley said, however, Washington made no formal application.

"There are no applications in relation to the U.S. letters of request [for mutual legal assistance]," Dudley said.

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The court had opened a hearing on the tanker and but delayed the proceeding to take up the U.S. application.

Semi-autonomous Gibraltar had already released the tanker's crew before the U.S. appeal.

British marines took the ship on July 4 on suspicions it violated the EU rules.

After the seizure of the Grace 1, Iran retaliated by taking the British-flagged oil tanker Stena Impero on July 19 in the Strait of Hormuz, a narrow waterway near Iran that's a vital transportation route for nearly a quarter of the world's oil supply. British foreign minister Dominic Raab denied this month reports of a deal to swap the vessels.

"We are not going to barter a ship that was detained legally with a ship that was detained illegally," Raab said. "That's not the way that Iran will come in from the cold."