The United States applied yesterday to seize an Iranian tanker in Gibraltar, halting its expected release at the last minute and preventing a possible swap for a British-flagged tanker held by Iran.
The Grace 1 oil tanker was seized by Royal Marine commandos in a landing in darkness off the coast of the British overseas territory on July 4.
Gibraltar said the tanker was suspected of selling oil to Syria in breach of European Union sanctions. Two weeks later, Iran's Revolutionary Guards seized the British-flagged Stena Impero in the Gulf.
Gibraltar was widely expected to release the Grace 1 yesterday, but just hours before, the US Department of Justice sought to seize it.
Gibraltar's government said that the matter would return to the supreme court.
The Gibraltar Chronicle newspaper said the court's chief justice, Anthony Dudley, made clear that were it not for the US move, "the ship would have sailed".
While both Britain and Iran deny they were planning to swap the vessels for each other, there has been widespread expectation that the British-flagged ship will not be freed until the Iranian tanker is released.