Donald Trump was in typically bombastic form as he stood on the White House lawn this week and described the latest wave of US sanctions on Iran as the strongest “our country has ever issued”. He made clear that he was winning and Iran had already been weakened. Nobody was talking any more about Iran taking over the Middle East, the US president said.

In some respects, he has a point. This week’s sanctions hit 700 Iranian targets, most importantly the Islamic republic’s ability to export oil, its economic lifeline. The economy has been reeling since Mr Trump defied his European allies and withdrew from the 2015 nuclear accord with Iran in May. The rial has collapsed, prices have soared and western companies rushed to pull out of the country.

Yet despite Trump officials’ promises to reduce Iran’s oil exports to zero, the administration issued six-month waivers to eight nations, including China, India, Japan and South Korea, which together accounted for the majority of the 2.7m barrels a day Iran sold in May. Mr Trump is clearly worried about prices at the fuel pump. The administration did not clarify how much countries could buy under the waivers, but the move gave at least a short term fillip to Tehran.