Bloomberg - Iran’s Foreign Ministry called in the South Korean ambassador last month to demand payment of 7 trillion won ($6 billion) for oil it sold to the Asian country, Chosun Ilbo reported, citing officials it didn’t identify.

Iran expressed “strong regret” over Seoul’s failure to complete the payment, which has been deposited at two South Korean banks without being transferred to Iran’s central bank for years due to U.S. sanctions against the Middle Eastern country, the newspaper said. It added that other Iranian authorities including the central bank also complained.

South Korea sent a delegation to the Middle East late last month and explained that the country will cooperate with the U.S. to successfully complete transfer of the payment, it added.