Tehran has refused to comment on the embarrassing revelation that China’s private ports are complying with a ban on Iranian shipping.

Ali Nazi, Deputy Director of Ports and Maritime Organization told ILNA news agency on Saturday that such “information is confidential.”

China has handed over most main ports to the private sector and foreign companies.

These operators do not allow Iranian ships to dock, for fear of being subject to US sanctions.

Iranian shipping can dock in Chinese government-controlled ports, but their inadequate facilities and equipment increase the loading and unloading time, while their locations increase voyage time and lead to higher costs.

China is a diplomatic ally of the Islamic Republic but so far it has avoided openly challenging US sanctions. While Beijing clandestinely imports hundreds of thousands of barrels of crude a day via third party channels, Iran gains little from the trade as intermediaries take most of the profits and often deliver goods instead of cash.

Official figures released by China's Customs show no direct oil purchase from Iran in 2021. But in March Bloomberg claimed that details from third-party sources indicated that Iranian oil was often re-branded as purchases from other countries and such exports had even surged.

The news about China’s compliance with US sanctions will be embarrassing for hardline supporters of Supreme Leader Ali Khamenei who have been trumpeting Iran’s “Looking East” policy.