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Israeli-Palestinian diplomacy brokered by the United States is rapidly heading toward a September crisis. President Obama and Prime Minister Benjamin Netanyahu need to establish a new understanding quickly when they meet Tuesday at the White House or relations between the two governments will remain stormy and efforts to launch direct negotiations will fail.

The Arab League has given Palestinian Authority President Mahmoud Abbas until mid-September to negotiate in "proximity talks," in which the United States acts as a go-between. Arab League Chairman Amr Moussa has declared that he will take the Israeli-Palestinian issue to the U.N. Security Council if there is no progress by that deadline. So far, both the Israelis and Palestinians are taking an approach that...