The government of Gibraltar is awaiting confirmation that the Iranian VLCC Adrian Darya 1 has breached EU sanctions by discharging its oil in Syria.
Iran has said the vessel unloaded the cargo in the eastern Mediterranean, while satellite pictures suggest it is lying off Tartus in Syria.
Doubts remain about whether the oil actually has been discharged, however.
"We will await the outcome of the meeting between the [UK] foreign secretary, Dominic Raab, and the Iranian ambassador to London before jumping to judgement," Gibraltar said.
The 301,000-dwt vessel (built 1997) was held in Gibraltar in July because authorities believed it was en route to Syria.
The ship was released when Iran pledged not to deliver the oil there.
Gibraltar said such an act would be "an egregious and contumelous breach of the undertakings given by Iran to Gibraltar in a formal, diplomatic Note Verbale."
"If the reports that the oil has been sold to Syria are true, it will render worthless the written word of the government of Iran on all matters," it added.
"The world will be better placed to judge Iran's position on other, more transcendental matters based on actions on this issue on which they have been under the microscope of international scrutiny."
Shifty?
The territory's chief minister Fabian Picardo said:"Gibraltar did its bit in relation to the Grace 1 to stop the vessel when we did. We held her here, in British Gibraltar Territorial Waters for 45 days.
"Now we await details of the final destination of the oil before making any further comment. It will be a massive volte face for Iran to have failed to live up to its written undertaking in the full glare of international public opinion. They will really make themselves look shifty and unreliable if they have acted contrary to their repeated assertions and undertakings."
