Kurdish Security Forces Iraq
A member of the Kurdish security forces guards a section of an oil refinery, being brought on a truck to Kalak refinery in the outskirts of Arbil, in Iraq's Kurdistan region, on 14 July.Reuters

US Marshals have been ordered to seize a cargo of oil from Iraqi Kurdistan on a tanker off the coast of Texas, according to court filings.

A judge signed the order after the Iraqi central government laid claim to the oil on board the United Kalavrvta tanker.

The tanker, which left the Turkish port of Ceyhan in June, is too large to enter the port at Galveston. It had been preparing to unload its cargo on to smaller boats that would transport the oil to the US mainland, after receiving clearance from the US Coast Guard.

The tanker is thought to be carrying around 1 million barrels of oil, worth about $100m.

Iraqi Kurdistan and the central government in Baghdad have been locked in a dispute over the autonomous region's right to sell oil independently.

Both sides claim that the Iraqi constitution permits them the rights to sell the oil.

Since a new pipeline linking Iraqi Kurdistan with Turkey was completed in 2013, Kurdish oil has begun to flow in greater volumes.

While the Kurds have successfully loaded a number of oil tankers, they have struggled to find buyers on international markets amid fierce opposition from Baghdad.

Iraq's central government has launched legal proceedings against Turkey for its role in aiding the Kurds to transport the oil. However, one tanker successfully unloaded at the Israeli port of Ashkelon in June, although the buyer remains unknown.

Baghdad insists it has sole right to export oil from all of its regions and that the Kurds' attempt to sell oil independently amounts to smuggling.