AP Photo

Egypt's mounting political and economic woes will cause many policy headaches for the Obama administration during the next four years. But in the short run, the Obama administration will have to confront a more immediate risk: that a major terrorist attack in the Sinai will catalyze a security crisis between Israel and Egypt, which the ruling Muslim Brotherhood may use as a pretext for downgrading Egyptian-Israeli relations and perhaps canceling the 1979 Egyptian-Israeli peace agreement altogether. To prevent this outcome, Washington should immediately press Egyptian President Mohamed Morsi to establish direct communication channels with the Israeli government to ensure that this kind of crisis will be managed responsibly.

A terrorist attack emanating from the...