The US has applied to take control of an Iranian oil supertanker which was seized by Royal Marines in Gibraltar, it is reported.
The ship's captain and three officers have been released from custody and are no longer subject to police investigation.
Gibraltar Supreme Court Justice Anthony Dudley said the "ship would have sailed" if not for America's fresh attempt to seize it just hours before it was to be released.
The vessel was seized in the Mediterranean in July and has remained in the British territory ever since amid escalating tensions between Iran and the West.
Britain had said the tanker was violating European sanctions by taking millions of barrels of crude oil to Syria, a charge Iran denies.
The application means that a decision on the fate of Grace 1 will not be made until later on Thursday, the Gibraltar Chronicle reported.
Tehran had claimed earlier this week that Britain could release the Grace 1 on Tuesday, but that did not happen.
The commandeering of the Grace 1 on July 4 escalated tensions between Tehran and the West and led to retaliatory moves in Gulf waterways used to ship oil.
Iran seized the UK-flagged Stena Impero oil tanker in the Strait of Hormuz for alleged marine violations two weeks later.
The deputy head of Iran’s Ports and Maritime Organisation, Jalil Eslami, said on Tuesday that Britain was thinking of freeing the Grace 1 following an exchange of documents.
He claimed the ship "was seized based on false allegations".
Although Grace 1 was seized by British forces, Britain said on Tuesday that investigations into the tanker Grace were a matter for Gibraltar.
The territory has denied Iran’s claim that the action was taken on the orders of Tehran’s longtime foe Washington.
Iran has denied the vessel was doing anything improper.
The Gulf tanker crisis has erupted after Washington pulled out of Iran’s 2015 nuclear deal, under which Tehran agreed to curb its nuclear work in return for lifting most international sanctions on Tehran.
Unlike the seized Iranian tanker, which was carrying a cargo of up to 2.1 million barrels of oil, the Stena Impero was on its way to the Gulf and empty at the time it was seized by Iranian forces.
