The humanitarian situation in Gaza has grown worse since a 5-month truce began coming apart two weeks ago. Responding to near-daily rocket attacks, Israel shut its cargo crossings with the territory. Ban - who called Prime Minister Ehud Olmert earlier this week to lobby for more aid shipments - turned up the heat on Thursday with a similar call to Foreign Minister Tzipi Livni.

In a tense conversation with Ban, Livni declared that the blockade would not end until Palestinian militants stop firing rockets at Israel, an aide to Livni reported.

"There is no way that Palestinian terrorists will shoot at us and we will not respond," Livni told Ban, the aide said. "The international community must speak up and use its influence against the Palestinian rocket attacks."

The aide spoke on condition of anonymity because the telephone call was private. There was no immediate word from the U.N. on Ban's appeal.

After a rocket was fired from Gaza, Israel's Defense Ministry said the crossings would remain closed on Friday.

Israel hopes by closing cargo crossings it can force Gaza's Islamic Hamas rulers to halt militant rocket and mortar fire at Israeli border towns. But the closures have drastically reduced the flow of goods into Gaza, home to 1.4 million people.

Although some food is smuggled in through tunnels from Egypt, many basic goods are in short supply.

The top U.N. aid official in Gaza told The Associated Press on Thursday that Israel had reversed a decision to let in 70 trucks of humanitarian aid, bringing U.N. aid stocks perilously close to depletion.

Israel denied it had agreed to let the aid through.

"We have pinpoint intelligence warnings that they are planning a terror attack on the crossings," said Israeli Defense Ministry spokesman Shlomo Dror. "The trucks were never supposed to go through because of the rocket attacks and because of the planned attack on the crossings."

Without more supplies, the U.N. will be forced to suspend food distribution to 750,000 Gazans at the end of the week, said John Ging, head of Gaza operations for the United Nations Relief and Works Agency.

"We have a situation where 80 percent of the population live in abject poverty and the results of that are the daily needs are not being met by any family," Ging said.

Nobel Peace Prize laureate Mairead Maguire said Thursday the U.N. should suspend or revoke Israel's membership.

During a visit to the West Bank, Maguire said Israel should be punished for ignoring U.N. resolutions over the years. Maguire won the 1976 peace prize for her work with Catholics and Protestants in Northern Ireland.

In the northern Gaza town of Beit Hanoun, Umm Attar, a 34-year-old housewife, cooked tomatoes in a battered saucepan set over a wood fire. Cooking gas hasn't entered Gaza since the violence renewed in early November, and Umm Attar said she couldn't afford black-market cooking gas prices - now $100 a tank.

"I can't serve cold food day after day. And what if my husband wants a cup of tea?" she asked, stirring the food as she shooed away flies.

Olmert and Israeli Defense Minister Ehud Barak made a secret trip this week to visit King Abdullah II of Jordan, who warned that a large-scale military operation in Gaza would destabilize the region, Israeli and Jordan officials disclosed on Thursday.

Hamas seized power in Gaza last year, expelling forces loyal to Palestinian President Mahmoud Abbas, who now controls only the West Bank. The rift has complicated Israeli-Palestinian peace talks.

The talks have produced no breakthroughs, and their future could be clouded by February parliamentary elections in Israel, where polls show hawkish Benjamin Netanyahu's Likud Party in the lead.

Abbas, meanwhile, took his case for a peace deal directly to ordinary Israelis on Thursday, assuring them in full-page, Hebrew-language newspaper ads that a withdrawal from all territories captured in the 1967 Mideast war would bring them full recognition by the Arab world.

This deal was first offered in the 2002 Arab Peace Initiative. The war-won lands include territories the Palestinians seek for an independent state.