Famine has been mostly averted in Gaza as a surge of aid enters the territory during a fragile ceasefire, the United Nations humanitarian chief said Sunday. But he warned the threat could return quickly if the truce collapses.

Israel completed its withdrawal from the Netzarim Corridor on Sunday, a militarized zone that splits Gaza in half, as part of its commitments under a ceasefire agreement with Hamas. Hundreds of thousands of Palestinians have filed through the area,

The withdrawal from the Netzarim corridor removes one of Israel’s bargaining chips as it moves toward negotiating a full end to the war.