If Trump and Saudi Arabia tinker with Iran as it teeters towards revolution...
The US president could convince Europe to join his cause and withdraw from the 2015 nuclear deal if the deadly crackdown escalates, but Iran’s leaders may gain more power once the dust settles

The protests could also tempt Saudi Crown Prince Mohammed bin Salman, with his chequered foreign policy track record, to embark on yet another risky adventure involving an effort to stir unrest among ethnic minorities in Iran, such as the Kurds, Baloch and Iranian Arabs. Prince Mohammed’s earlier attempts to stymie Iranian influence in the Middle East sparked his ill-fated military intervention in Yemen and failed attempt to force Lebanese Prime Minister Saad Hariri to resign.

This month Trump not only has to decide whether to certify to Congress that Iran has complied with the 2015 international agreement that curbed its nuclear programme, but also whether to waive US sanctions. A decision to reimpose economic sanctions could mean a US withdrawal from the agreement. In October, Trump refused the quarterly certification.