Speaking to some 6,500 assembled for the conference, Robert Satloff, the executive director of the Washington Institute for Near East Policy, warned of “the potential for a deep disagreement between the U.S. and Israel governments over how to really deal with a nuclear Iran.” The issue could produce “the most tense face-to-face disagreement between the United States and Israel in the past 61 years,” he said. Other close observers of the relationship say its contours remain unclear. “Barack Obama still has to prove himself to American friends of Israel, who still don’t know where his heart is on Israel,” said a Democratic member of the House of Representatives. “And Bibi has to prove he is up to this moment.”