Turkey is not easily able to diversify its oil imports, Foreign Minister Mevlüt Çavuşoğlu said on Thursday, after US waivers for sanctions on oil purchases from Iran ended, Reuters reported.

Speaking at a news conference Çavuşoğlu said Turkey’s refineries are not “suitable” for other countries’ oil, adding that Washington should review its decisions on the issue.

Iran is one of the biggest suppliers of oil to Turkey, which is almost completely reliant on imports to meet its energy needs.

The United States demanded on April 22 that buyers of Iranian oil stop purchases by May 1 or face sanctions, ending six months of waivers that had allowed Iran’s eight biggest customers, most of them in Asia, to import limited volumes.