New satellite photos obtained Tuesday show an Iranian oil tanker pursued by the US remains off the coast of Syria.
The world will judge Iran if they have breached their undertaking not to sell the Grace 1 oil to Syria, says the Chief Minister, who nevertheless said the Gibraltar Government would be waiting for the results of meetings between the United Kingdom and Iran before jumping to judgement.
Tehran, desperate for revenue from oil exports, did not formally confirm that the customer was Syria.
Foreign Secretary Dominic Raab said it was clear the tanker had transferred its cargo in Syria.
"This sale of oil to (Syrian President Bashar al-Assad's) brutal regime is part of a pattern of behaviour by the Government of Iran created to disrupt regional security".
"Iran's actions represent an unacceptable violation of worldwide norms", the statement said.
The Adrian Darya 1 vessel, formerly named Grace 1, was seized by British Royal Marine commandos on July 4 on suspicion of heading to Syria. In mid-August, a Gibraltar court ordered the vessel's release against USA objections, after authorities said they had received assurances from Iran that the ship would not proceed to Syria.
The US vowed on Sunday to impose sanctions on any buyer of the 2.1 million barrels of Iranian crude oil on board.
The Iranian tanker detained by British forces was later released and Iran has since freed seven of the 23 crew members of the Swedish-owned British-flagged Stena Impero tanker - one Russian, one Latvian and five Indian nationals.
Britain, meanwhile, said Tuesday it's clear the tanker delivered its cargo to Syria in violation of worldwide sanctions.
The US attempted to block the departure of the ship from Gibraltar, and US administration officials then tried to contact the captain of the ship to offer him a substantial sum in return for not selling the oil to Syria but instead taking the ship to a port at which the US could seize the 2.1m tonnes of oil.