Tehran has taken a hardline on resuming the deal and he warned that Washington will enforce the sanctions “so long as Iran refuses a mutual return to full implementation” of the deal. The Treasury Department said that under the sanctions, all the properties and interests in the US of the eight companies or those in which they have at least 50 per cent interest “must be blocked” and reported to its Office of Foreign Assets Control (OFAC).

This applies also to any Americans who may have control over the assets of those companies and persons involved in certain transactions with them could also face sanctions or enforcement actions, the Department said.

It added that Tibalaji bought “petrochemical products, including methanol and base oil, for onward shipment to China” through deals brokered by Triliance Petrochemical Co. Ltd. Network that had been sanctioned earlier. Triliance is based in Hong Kong with branches in Iran, China and the UAE.