MADRID - (AP) -- The United States moved on Thursday to seize an Iranian supertanker detained in Gibraltar for breaching international sanctions on oil shipments, thwarting efforts by authorities in London and the British overseas territory to defuse tensions with Tehran.
The Gibraltar government confirmed earlier media reports that the U.S. Department of Justice had sought to extend the detention of the oil tanker Grace 1, prompting the Supreme Court in the territory to adjourn a scheduled decision on whether to release the ship until later in the day.
"The U.S. Department of Justice has applied to seize the Grace 1 on a number of allegations which are now being considered," the government said in a statement, adding that the matter would be reviewed by the court at 4 p.m. local time.
The Justice Department did not immediately respond to a request for comment. Britain's Foreign Office said in a statement that the "investigations conducted around the Grace 1 are a matter for the government of Gibraltar" and that it could not comment further as the investigation was ongoing.
While there was no immediate reaction from Tehran, the U.S. move likely will further stir tensions in the Persian Gulf.
The detention of the Grace 1 saw Iran seize the British-flagged oil tanker Stena Impero, which remains held by the Islamic Republic. Analysts had hoped the release of the Grace 1 by Gibraltar would see the Stena Impero similarly released.
The Grace 1 was seized last month in a British Royal Navy operation off Gibraltar. The vessel was suspected of violating European Union sanctions on oil shipments to Syria, and its seizure deepened international tensions in the Persian Gulf.
The Gibraltar government had said it was seeking to "de-escalate" the situation over the Grace 1.
Speculation on the impending released had mounted around Thursday's hearing at the Gibraltar Supreme Court. But a lawyer representing the territory's General Attorney Michael Llamas said the U.S. had moved at the eleventh hour.
The Gibraltar Chronicle reported that the captain and three officers of the Grace 1 had been released from arrest on Thursday, but the report could not be confirmed. A Gibraltar government spokesman declined to comment.
Speaking in court, Chief Justice Anthony Dudley said that were it not for the U.S. move, "the ship would have sailed," the Chronicle reported.
Tensions have escalated in the region since President Donald Trump over a year ago unilaterally withdrew the U.S. from Iran's 2015 nuclear deal with world powers. The decision stopped billions of dollars' worth of business deals, largely halted the sale of Iran's crude oil internationally and sharply depreciated Iran's currency, the rial.
In recent weeks, Iran has begun to step away from the nuclear deal by increasing its production and enrichment of uranium. It has threatened to take further steps in early September if Europe can't help it sell its oil abroad.
Gambrell reported from Dubai, United Arab Emirates. Associated Press writer Jill Lawless in London contributed to this report.
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