Greece has said it will not endanger its relations with the US by aiding an Iranian supertanker sought by the US but released by Gibraltar.
The Adrian Darya 1, previously named Grace 1, is in the Mediterranean Sea believed to be heading for a Greek port.
An Iranian news agency has corrected an earlier report in which it stated the vessel was currently leased to Iran's elite military force.
It now says the tanker is in fact being leased to an Iranian shipping company.
After being seized last month by Royal Marines off Gibraltar, the Adrian Darya 1 left the British Overseas Territory late on Sunday after being detained for a month for allegedly trying to breach European Union sanctions on Syria.
Gibraltar authorities rejected attempts by the US to seize the oil tanker again, arguing that EU regulations are less strict than US sanctions on Iran.
Gibraltar says it has been assured by Iran that the tanker would not unload its cargo in Syria.
Greek deputy foreign minister Miltiadis Varvitsiotis said Athens is under pressure from US authorities, which claim the Iran-flagged Adrian Darya 1 is tied to a sanctioned organisation.
He told Antenna TV that the 1,000ft tanker is too big to enter any Greek port and cannot legally unload its $130million worth of light crude oil at EU refineries.
The vessel can still enter Greek waters or anchor offshore, in which case Athens will "see" what it will do, Mr Varvitsiotis added.
The tanker's release comes amid a growing confrontation between Iran and the West after US President Donald Trump pulled Washington out of Tehran's nuclear deal with world powers over a year ago.
Shortly after the tanker's detention in early July, Iran seized the British-flagged oil tanker Stena Impero, which remains held by the Islamic republic.