Which was carrying one million barrels
Iraqi Kurdistan has exported at least eight million barrels of oil since May, energy experts told Al Arabiya News.
But the increasingly weak regime in Baghdad is trying to keep control of its oil billions and says the Kurdish regime cannot sell the oil in the U.S.
The U.S. Coast Guard's AIS c for the United Kalavrvta on Thursday, which was carrying one million barrels - and was 95 per cent - when it went dark.
The tanker was attempting to unload its cargo at sea, off the coast of Texas, after leaving the Turkish port of Ceyhan in June and anchoring near the U.S. port of Galveston in late July.
The U.S. Coastguard confirmed to MailOnline today that the last contact the agency had with the United Kalavyrta was when the ship's certificate of compliance was completed on July 27.
The vessel's disappearance is now thought to be the latest development in a high-stakes dispute between Baghdad and the Kurds over the right to export oil.
Several other tankers transporting disputed oil from Iran or Kurdistan have switched off their transponders before unloading their cargo - making their movements extremely difficult to track.
A Coast Guard official told MailOnline today that the vessel might have turned off its beacon in the Gulf of Mexico, which it is not supposed to do.
The official also said it was possible the ship had traveled outside the range of the U.S. Coastguard antennas which would account for it vanishing from the AIS ship-tracking system.