Turkey's sole refiner Tupras, a unit of Koc Holding, said in a statement to the Istanbul stock exchange that it would cut its purchases of Iranian crude by 20%. Tupras is the main Turkish customer, currently buying some 30% of its crude oil from Iran, and it has an 9 million tonnes annual purchase contract. Koc Energy Group Chairman Erol Memioglu told reporters last month that the existing Tupras oil contract with Iran ends in August. He said that he expected more clarity on the details of the sanctions in May, before Washington's measures on oil-related transactions take effect on June 28. Both the United States and the European Union have imposed unilateral sanctions against Iran's financial and energy sectors over its nuclear programme, whereas Turkey has said it is only compelled to observe the softer U.N. sanctions.