The U.S. Department of Treasury on Thursday imposed sanctions on a network of more than a dozen people and firms that are accused of facilitating the shipment of millions of barrels of Iranian oil to China.

The opening shot of Trump's rebooted "maximum pressure" campaign against Iran comes after the president suggested this week that its leaders should "immediately" work with the US on a new nuclear agreement.

Iran's oil minister said imposing unilateral sanctions on crude producers would destabilise energy markets, the ministry's SHANA news outlet reported on Wednesday, after U.S. President Donald Trump said he would seek to drive Tehran's oil exports to zero.