Egypt's President Abdel Fattah al-Sisi has said he rejects the forced displacement of Palestinians into the Sinai peninsula as the first aid convoy entered Gaza after two weeks of war.
Speaking at a summit in Cairo, Mr Sisi said the only solution was an independent state for Palestinians.
The summit began as 20 trucks carrying aid crossed the Rafah border.
However humanitarian organisations have warned it will not be enough to address the need.
About 500 trucks a day had been entering Gaza before the war started. Some 1.2 million people living in the territory already relied on food aid, the UN says.
The UN will be responsible for distributing the aid, with much of it likely to be sent to UN schools where thousands have been sheltering and hospitals.
One of the trucks was loaded with coffins, a BBC reporter watching the trucks enter Gaza reports.
Afterwards US President Joe Biden expressed his "deep personal appreciation" to Egypt, Israel and the UN for allowing the aid to get through.
"We will continue to work with all parties to keep the Rafah crossing in operation to enable the continued movement of aid that is imperative to the welfare of the people of Gaza," his statement said.
Israel's military said the aid was for southern Gaza only and repeated calls for residents in the northern Gaza Strip to leave their homes.
They should move south of Wadi Gaza in the centre of the territory, it said.
It has vowed to wipe the Hamas "off the face of the earth".
However in his speech at the Cairo-hosted "Summit for Peace", Mr Sisi said his country would not allow Palestinians to be displaced across the Rafah crossing into Egypt.
His comments were backed by Saudi Foreign Minister Faisal bin Farhan Al-Saud.
Mahmoud Abbas, who is head of the Palestinian Authority which has control over areas of the occupied West Bank but not the Hamas-run Gaza Strip, also said Palestinians could not be forced to leave.
"We will never accept relocation, we will remain on our land whatever the challenges," he said.
The summit broke up without a joint statement.
No Israeli or senior US officials were present, and differences between Arab and European countries were stark.
According to Arab diplomats quoted by AFP on condition of anonymity, European delegates demanded "a clear condemnation placing responsibility for the escalation on Hamas" but Arab leaders refused.
At the end, Egypt released a statement approved by Arab delegations, criticising world leaders for seeking to "manage the conflict and not end it permanently".
Egypt and other Arab states have previously said an influx of Palestinian refugees fleeing the war would be unacceptable because it would amount to the expulsion of Palestinians from their land.
Meanwhile King Abdullah of Jordan denounced what he called "global silence about Israel's attacks on Gaza".
"The message the Arab world is hearing is that Palestinian lives matter less than Israeli ones," he said.
UK Foreign Secretary James Cleverly told the leaders in the summit that he had spoken to the Israeli government about its duty to respect international law and to preserve civilian lives in Gaza.
"Despite the incredibly difficult circumstances, I have called for discipline and professionalism and restraint from the Israeli military," he added.
Mr Cleverly added that the international community needed to work to prevent the situation in Gaza provoking a regional conflict.
During his address to the summit, UN Secretary General Antonio Guterres called for a "humanitarian ceasefire" in the war, demanding global "action to end this godawful nightmare".
The Palestinians need "a continuous delivery of aid to Gaza at the scale that is needed", he said.
Israel began retaliatory air strikes on Gaza after an attack by Hamas's military wing on Israel on 7 October killed 1,400 people, many in their homes in kibbutzes near Gaza and at a music festival that was happening nearby.
Israel says more than 300 soldiers were also killed in the attack and Hamas took more than 200 hostages into Gaza.
The Hamas-run health ministry in Gaza says that more than 4,300 people have been killed in Israeli air strikes, more than half of them women and children.