US demanded that Iranian oil buyers stop purchases by May 1 or face sanctions The decision was more stringent than expected, and caught several key importers to plead with the US ANKARA: Turkey is trying to convince the United States to allow refiner Tupras, its biggest oil importer, to continue buying crude oil from Iran free of sanctions, Foreign Ministry spokesman Hami Aksoy said on Friday. Washington on Monday said it will not renew exemptions granted last year to buyers of Iranian oil, including Turkey, and it demanded that buyers stop purchases by May 1 or face sanctions. The decision was more stringent than expected, and caught several key importers who have been pleading with Washington to continue buying Iranian oil sanctions-free.