Greece said on Wednesday that it would not give a safe haven to the Grace 1 oil tanker in Iran after the US threatened to impose sanctions on every state that helped the ship.
The Iranian oil tanker left Gibraltar the weekend after a month in British captivity and was heading east across the Mediterranean to the Greek port of Kalamata.
The US warned Athens that this could have diplomatic and economic consequences if it helped the ship, which carries around 2 million barrels of oil.
"We made it clear that anyone who touches it, anyone who supports it, anyone who allows a ship to dock, runs the risk of receiving sanctions from the United States," said Mike Pompeo, US Secretary of State.
Hours after Mr. Pomepeo's warning, Greece announced that the ship was not welcome to dock at Greek ports or unload its cargo of $ 130 million.
Miltiadis Varvitsiotis, the Deputy Minister of Foreign Affairs, said the 1000-foot ship was too large for a Greek port and said that Greece would abide by EU sanctions against oil transportation to Syria.
"We are sending a message that we are not prepared to facilitate the course of this ship to Syria," Varvitsiotis said. "And this is a message that we have made very clear."