Chinese oil firms will again buy crude oil from Iran and are seeking to increase their imports from the country.

A senior Iranian official has confirmed that Chinese state firms are carrying on business with the world's fourth-largest oil producer, despite U.S calls for international businesses to reduce business ties with Iran.

China has said sanctions are not the way to resolve the row over the Iranian nuclear program and it will continue to negotiate with Iran in order to increase crude oil purchases.

China is currently purchasing about 400,000 barrels per day from Iran.