In the Persian Gulf, tensions are rising over the sanctions recently imposed by the US on Iran in the wake of its refusal to comply with Washington’s demand that the nuclear agreement signed by Barack Obama be reopened. Tehran does not wish to submit to this demand, as it would suggest weakness on the part of the regime and would inhibit Iran’s nuclear ambitions. But its refusal could lead to the collapse of the Iranian economy, war, and possibly the overthrow of the regime.