Iran’s president said Wednesday the United States made a “stupid mistake” by abandoning a nuclear deal and warned of severe consequences if its allies agree to extend an arms embargo. The United States is waging a campaign to extend the ban on selling conventional weapons to Iran, which is set to be progressively eased starting in October. The ban is to be lifted in accordance with UN Security Council Resolution 2231, which blessed the landmark international agreement that placed limits on Iran’s nuclear programme in 2015.