America’s chief nuclear negotiator believes that some U.S. allies and members of Congress don’t want diplomacy with Iran to succeed. The undersecretary of state for political affairs, Wendy Sherman, concedes the nuclear talks are controversial. She says some fear they’ll collapse while others fear they’ll succeed. Speaking at the Center for Strategic and International Studies, Sherman says the administration has sought to allay fears in Congress and among allies including Israel and Arab Gulf states. She says the conversations reinforce her government’s conviction that diplomacy is worth the risk. Negotiators want a deal by Nov. 24. World powers are seeking limits on Iran’s program so it can’t produce nuclear weapons. Iran says it wants to generate nuclear energy and is asking for sanctions relief.