The United Nations humanitarian chief is in Gaza, surveying the damage after a 22-day Israeli offensive against the Palestinian territory's Hamas rulers.

John Holmes is touring the Gaza Strip Thursday to assess how the U.N. can best help the territory's 1.5 million people.  Holmes has said reconstruction efforts likely would cost billions of dollars.

Israeli ground, air and sea attacks on Gaza caused widespread shortages of power, food and water, and damaged schools, mosques and hospitals.

Thirteen-hundred Palestinians and 13 Israelis died in the operation Israel said was aimed at stopping Hamas militants from attacking the Jewish state.

Senior Israeli defense official Amos Gilad traveled to Cairo Thursday to meet Egyptian officials who have been trying to mediate a long-term truce between Israel and Hamas.

The two sides declared unilateral cease-fires on Sunday, ending major combat.

Israeli Foreign Minister Tzipi Livni warned Thursday that Israel may resume military action to prevent smugglers from helping Hamas to rearm.

Smugglers have used tunnels to transport weapons as well as civilian goods, like food, into Gaza from Egypt.  Hundreds of Palestinians gathered Thursday to try to repair the tunnels damaged by Israeli strikes.

In another development, Israeli media say the government is preparing to be more flexible in negotiations with Hamas on a prisoner exchange.

Israel is trying to secure the release of an Israeli soldier held in Gaza, while Hamas wants Israel to free more than 1,000 Palestinian detainees, many of them militants.

Some information for this report was provided by AFP, AP and Reuters.