The US on 7 August reimposed a slew of sanctions on third-party dealings with Iran. The measures will hit Iran hard. But worse is to come with the US aiming to halt Iran’s oil exports from November.

Since announcing on 8 May that he was withdrawing the US from the 2015 Iran nuclear deal, known as the Joint Comprehensive Plan of Action (JCPOA), President Donald Trump has wasted no time in going on the attack.

On 7 August US reimposed the first batch of sanctions it had lifted under...