Previously known as Grace 1, the vessel was seized in July by British marines and held in Gibraltar for six weeks, on suspicion it was delivering oil for Tehran's ally Damascus. "It was a big mistake to trust Zarif", Pompeo said in a Twitter post, adding that Iranian Foreign Minister Mohammad Javad Zarif earlier "guaranteed to the United Kingdom that the IRGC oil tanker Grace1 / AdrianDarya1 would not head to Syria.".
The Adrian Darya has changed course several times since its liberation, initially appearing to set sail for Greece only to change course after the United States warned Athens that harboring the vessel would be seen as "supporting terrorism".
He added that it was "a big mistake" to trust any assurances about the ship from Iranian Foreign Minister Javad Zarif.
"Anyone providing support to the Adrian Darya 1 risks being sanctioned", warned Sigal Mandelker, US Under Secretary for Terrorism and Financial Intelligence. The vessel's detention and later release by Gibraltar has fueled the growing tensions. The tanker then headed for Mersin in Turkey, changed course for Cyprus - only to head back toward the Turkish port of Iskenderun.
However, mariners can input any destination into the AIS, so Turkey may not be its true destination. Earlier, it said it was going to Greece.
After the vessel was impounded on July 4, Washington had pressured Gibraltar, a British territory on the southern tip of Spain, to keep the tanker and its cargo of 2.1 million barrels of oil, impounded.
The Office of Foreign Assets Control added the ship, formerly called Grace 1, and its captain Akhilesh Kumar to its Specially Designated Nationals list on Friday as the tanker's destination changed from Turkey to Lebanon.
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Turkey's Iskenderun port is 200 km (124 miles) north of Syria's Baniyas refinery, the tanker's suspected original destination. "And we follow actually very closely.it is heading to Lebanon", Cavusoglu said. She also said Lebanon does not have a refinery to deal with crude oil.
It also said it could not name the actual destination due to "economic terrorism" by the United States and its sanctions on Iran's oil sales.
However, Lebanon's Finance Minister Ali Hassan Khalili told Reuters, "We have not been informed of the Iranian oil tanker Adrian Darya heading (here)".
Oil sector experts believe Iran is still planning a ship-to-ship transfer of the oil, with Syria being a likely final port of call.
An Iranian government spokesman was quoted on Monday as saying Iran had sold the oil aboard the tanker and that the vessel's owner, whose identity he did not disclose, would decide its destination.
Analysts have suggested Iran may choose to offload the oil onto another ship first, given the worldwide attention focused on the vessel.