U.S. and Iranian negotiators set to resume talks Monday are hoping to seal a tentative political agreement on Tehran’s nuclear program, though Western diplomats said serious negotiations over substance would still be needed in the months ahead. An announcement of a political agreement before an end-of-March deadline, could spur expectations that Iran and the six-nation group is on track for a deal—an advance they hope would buy them fresh time to reach a final, detailed nuclear accord by June 30. Any such political understanding that emerges in the coming days would fall short of the goal the two sides set when the diplomacy was extended in November to complete the negotiations by the end of March. Secretary of State John Kerry arrived in Switzerland on Sunday ahead of meetings with […]