CAIRO — A sharp deterioration in Egypt’s relations with Israel is further complicating Washington’s faltering efforts to move the Middle East peace process forward.

The U.S. has long relied on Egypt’s key role as a mediator in the region, most crucially in trying to reconcile rival Palestinian factions. But those efforts are now stalled as U.S. Secretary of State Hillary Clinton rushes to Cairo to meet Egyptian President Hosni Mubarak on Wednesday — a clear sign of concern that Egyptian and Arab support for the Israeli-Palestinian peace efforts may be waning.