Iran and six world powers ramped up the pace at Tuesday’s negotiations over a preliminary deal on the Iranian nuclear program, as their self-imposed deadline approached and both sides warned it was crucial to overcome differences that could wreck an agreement. For nearly a week, the United States, Britain, France, Germany, Russia and China have been trying to break an impasse in the negotiations, which are aimed at stopping Iran from gaining the capacity to develop a nuclear bomb in exchange for easing international sanctions that are crippling its economy. But disagreements on enrichment research and the pace of lifting sanctions threatened to scupper a deal that could end a 12-year standoff between Iran and the West over Tehran’s nuclear ambitions and reduce the risk of another Middle East war. “We need to get this done now,” a Western official told Reuters on condition of […]