Israel and the Palestinian militant group Hamas agreed to a 12-hour humanitarian truce in the embattled Gaza Strip to begin on Saturday, but a more ambitious one-week cease-fire eluded American negotiators.

Israel on Friday rejected the longer cease-fire, thwarting the main goal of U.S. Secretary of State John Kerry during nearly a week of shuttle diplomacy in the Middle East and raising the prospect of an expanded conflict after 18 days of fighting that has left more than 900 dead, mostly Palestinians.

...