Iranian tanker spotted off Syrian port despite assurances Tehran would not flout EU sanctions

US National Security Advisor John Bolton says anyone who had believed ship would not continue on to Syria were 'in denial'

Satellite imagery appears to show the once-detained Iranian oil tanker Adrian Darya-1 near the Syrian port, despite U.S. efforts to seize the vessel (AP)

An Iranian tanker that sparked a diplomatic standoff between Tehran and western states has been spotted off the coast of Syria according to US officials – despite assurances the vessel would not deliver its 2.1 million barrels of crude oil to the country.

British royal marine commandos had previously detained the Adrian Darya 1 – then called the Grace 1 – off the coast of Gibraltar in July amid concerns it was being used to transport crude oil to Syria, sidestepping European Union sanctions on the country.

The vessel was released following written assurances from Tehran that it would not deliver the oil to the country.

However, after appearing to have turned off radio trackers in the eastern Mediterranean on Monday, satellite imagery has shown the vessel two nautical miles from the port of Tartus, western Syria, according to US officials.

Donald Trump's National Security Advisor John Bolton has since claimed that those who had believed the ship would not continue on to the country were “in denial”, following a continued campaign from Washington to seize the vessel.

The US Treasury Department blacklisted the tanker on Friday after warnings from Washington that any nation assisting the Adrian Darya 1 would be viewed as showing support for a terror organisation – specifically Iran’s Islamic Revolutionary Guard Corps.

Writing on Twitter, Mr Bolton added: “Tehran thinks it’s more important to fund the murderous Assad regime than provide for its own people. We can talk, but Iran’s not getting any sanctions relief until it stops lying and spreading terror”

The detaining of the vessel by UK authorities became a flash point in tensions between Iran, the US and the EU as the Middle Eastern state looks to fight back against tough sanctions levied by Washington after the breakdown of the Iran nuclear deal.

In an apparent show of retaliation for the Adrian Darya’s detention in Gibraltar, Iran seized a British-flagged tanker, the Stena Impero, two weeks later for alleged marine violations. So far the state has released seven of the ship’s crew, with a further 16 still left aboard.

And on Saturday the Iranian coast guard seized a vessel carrying 284,000 litres of diesel for allegedly smuggling fuel in the Gulf, detaining 12 crew members from the Philippines in the process.

The nation has been fighting rampant smuggling heightened by the decline of the Iranian Rial and the low price of fuel brought about by heavy state subsidies introduced to keep the nation competitive amidst international pressure.