UN chief António Guterres pleaded on Saturday for a "humanitarian ceasefire" in the war that has devastated much of Gaza, demanding "action to end this godawful nightmare".
Addressing a Cairo summit as the conflict raged into its third week, Guterres said the Palestinian enclave of 2.4 million people was living through "a humanitarian catastrophe" with thousands dead and more than a million displaced.
Israel is waging a relentless and indiscriminate bombing campaign against Gaza which has so far killed more than 4,300 people. It comes after Hamas militants stormed across the border into Israeli territory on 7 October, launching an attack that killed over 1,400 people.
"We meet in the heart of a region that is reeling in pain and one step from the precipice," he told the meeting that included the leaders of Egypt, Iraq, Jordan and the United Arab Emirates as well as of Italy and Spain and Palestinian President Mahmoud Abbas.
Guterres said "the grievances of the Palestinian people are legitimate and long" after "56 years of occupation with no end in sight" but stressed that "nothing can justify the reprehensible assault by Hamas that terrorised Israeli civilians".
He then stressed that "those abhorrent attacks can never justify the collective punishment of the Palestinian people".
Jordan's King Abdullah II called for "an immediate end to the war on Gaza" and condemned what he labelled "global silence" on Palestinian death and suffering.
"The message the Arab world is hearing is loud and clear: Palestinian lives matter less than Israeli ones. Our lives matter less than other lives," he said.
"The application of international law is optional. And human rights have boundaries – they stop at borders, they stop at races, and they stop at religions."
The summit came on the day a first contingent of aid trucks rumbled into southern Gaza, which Guterres said needed to be rapidly scaled up, with "much more" help sent through.
The UN has said that about 100 trucks per day are needed to meet worsening needs in Gaza.
The Palestinians need "a continuous delivery of aid to Gaza at the scale that is needed", the UN chief told the Cairo "Summit for Peace".
Egypt's President Abdel Fattah Al-Sisi said the "only solution" to 75 years of Israeli-Palestinian conflict is "justice".
"Palestinians must realise their legitimate rights to self-determination" and "an independent state on their land," Sisi said.
Abbas also called for a two-state solution and an "end to Israel's occupation" and rejected what he has warned could be a "second Nakba" ("catastrophe" in Arabic), a reference to the more than 750,000 Palestinians ethnically cleansed alongside the 1948 creation of Israel.
"We will not leave," he repeated three times at the end of his speech.
Cairo and Amman have repeatedly rejected calls for large numbers of refugees to enter Egypt from Gaza, warning the fresh "forced displacement" of Palestinians would lead to the "eradication the Palestinian cause".
Egypt and Jordan were the first Arab states to normalise relations with Israel, in 1979 and 1994 respectively, and have since been key mediators between Israeli and Palestinian officials.
But diplomatic efforts have so far made little headway and focused on getting humanitarian aid into the war-torn enclave where Israel has imposed a total siege, cutting off supplies of water, electricity, fuel and food.