The plunge in global energy prices and the rise of Islamic State militants have emerged as wild cards in the international diplomatic effort aimed at curbing Iran’s nuclear program, said U.S. and European officials. Negotiators concluded two days of talks here on Thursday aimed at reaching a final deal to curtail Tehran’s nuclear capabilities in exchange for an easing of international sanctions by a Nov. 24 deadline. “It is narrowing,” said Iranian Foreign Minister Javad Zarif about the differences between Iran and the bloc of nations at the talks. “But we still have a long way to go.” During the talks, economics and regional security arose as potential factors. Iran’s finances already have been sent reeling over the past two years due to international sanctions that have cut Tehran’s oil exports in half.