Both Turkey and South Korea have asked for waivers from the US to exempt their big refiners from recent sanctions imposed on Iranian oil exporters, according to reports.

The new law was made to prevent trade with Iran who are accused of building nuclear weapons but allows the issue of waivers to firms in countries that reduce or mean to reduce dealings withIran.

Iran recently warned it could shut the Strait of Hormuz, an important global shipping channel, if sanctions were imposed on its crude exports.