Iran and the United States could invest jointly in oil and gas development as part of the new nuclear deal the two are currently negotiating, an official from Tehran’s foreign ministry said Sunday, in the latest signal that Iran is willing to close a deal with the U.S. and avoid war. “For the sake of an agreement's durability, it is essential that the U.S. also benefits in areas with high and quick economic returns,” Hamid Ghanbari, deputy director for economic diplomacy at the Iranian foreign ministry, said, as quoted by the…