A former US national security official Mark Pfeifle has told Al Jazeera that Washington hopes it will not have to impose secondary sanctions on Chinese buyers of Iranian crude.

“I think that Trump and his Treasury Department will hold that in their back pocket as something they need to do if it becomes necessary,” Al Jazeera quoted him as saying.

Pfeifle said that broad measures against Beijing would be diplomatically difficult because the two economies remain intertwined, and that the aim for now was to make China more comfortable buying oil elsewhere.

Chinese refiners have bought sanctioned Iranian crude at a discount, he said, an advantage against their global competitors. He added that Beijing had shown no interest in helping Washington and was probably assisting Tehran quietly.

“The Chinese are playing the long game. They have no problem seeing the Americans tied up in another international excursion such as this war in Iran,” the report quoted him as saying.