The Islamic State (IS) is selling most of its illegally acquired oil through Turkey and Kurdish areas, according to a former counterterrorism officer with the Central Intelligence Agency, reported Russia Today.

In an interview with Russia’s Sputnik news agency, John Kiriokou said the illegal oil sales could be stopped if Washington made this a priority, but the US has chosen to focus on other areas.

“It’s a question of priorities. They have never allocated enough resources to do so. Other goals and missions have been rated as having more urgent calls on intelligence and tactical resources,” said Kirioku.

He said oil sales were not being facilitated by the Turkish government, but by “corrupt elements of the Turkish military and officials in local and regional governments in southwest Turkey.”

According to Kirioku, someone on the Turkish side of the border is making money out of the arrangement. “There are too many vested interests involved for it to stop. They greased the right people,” he said.

The US Treasury Department told Sputnik previously that IS makes about $40m each month on oil sales, amounting to around $500m per year.

Iraq has lost up to 400,000 b/d as a result of the advance of IS, the Iraq Oil Ministry spokesman Assem Jihad told the news agency.