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The UN Secretary General on Friday warned that the relocation of more than one million people from northern Gaza is “extremely dangerous” and “not possible”, while the US President said he was “urgently” addressing the humanitarian crisis.
The Israeli military issued an evacuation notice giving people in northern Gaza 24 hours to leave, promising not to attack an evacuation route for a short time.
Israeli commandos meanwhile conducted raids in Gaza ahead of an expected full-scale invasion to fight Hamas after the militants' attack last weekend.
“Moving more than one million people across a densely populated war zone to a place with no food, water or accommodation, when the entire territory is under siege is extremely dangerous – and in some cases simply not possible,” UN chief Antonio Guterres said.
The Israeli military is retaliating after Hamas militants killed more than 1,300 people in Israel and took scores more hostage.
The US has repeatedly stressed its full support for its ally and is shipping munitions to the Israeli military.
But the mounting death toll in Gaza, where about 1,800 people have been killed in air strikes, is becoming an increasing concern globally and is complicating the White House's messaging of outright support for Israel.
“We're making sure Israel has what it needs to defend itself and respond to these attacks,” US President Joe Biden said on Friday.
“It's also priority for me to urgently address the humanitarian crisis in Gaza and at my direction our teams are working in the region … We can't lose sight of the fact that the overwhelming majority of Palestinians have nothing to do with Hamas, and Hamas's appalling attacks, and they're suffering as a result as well.”
White House National Security Council spokesman John Kirby called Israel's demand for so many civilians to leave a “tall order”.
“We want to see that people have the ability to leave Gaza, and that's not the case right now,” he said on MSNBC.
Israeli Prime Minister Benjamin Netanyahu gave a brief address on TV on Friday, stressing Israel's “unity” against Hamas. He said the war against the militant group will “take time” but that Israel will come out the “victor”.
“I emphasise that this is only the beginning,” he said.
Secretary of State Antony Blinken on Friday said the US was working with international organisations to ensure civilians in the Gaza Strip are safe ahead of any potential invasion.
“We’ve urged the Israelis to use every possible precaution to prevent harming civilians,” Mr Blinken said after meeting Qatar’s Prime Minister Sheikh Mohammed bin Abdulrahman in Doha.
The UN has urged Israel to reverse its evacuation order on Gaza, arguing that so many people trying to flee would be “calamitous”.
Gilad Erdan, the Israeli ambassador to the UN, defended the evacuation notice and accused the world body of putting “its head in the sand” in the build-up to the Hamas attack.
“As resources and funds poured into Gaza and went straight into Hamas terror coffers, the UN stayed silent,” Mr Erdan said.
“Now that Israel gives Gaza civilian population advanced warning to evacuate areas, as we cherish life and do all what we can to minimise civilian casualties, the UN prefers to condemn these preventive measures.”
Mr Kirby later told reporters that the White House is routinely speaking with the Israeli government about “issues regarding the law of armed conflict”, noting “there was no prior consultation” with Israel about the evacuation notice.
The potential Israeli ground invasion comes amid its complete siege on densely populated Gaza this week that has left residents without food, water, electricity and fuel. Half of Gaza's residents are children.
Collective punishment is a war crime banned by the Geneva Conventions.
“We want to make sure humanitarian assistance continues to flow into Gaza and for the innocent Palestinian people that are there,” Mr Kirby added.
He also announced that the first State Department charter flight to Israel was en route “to assist US citizens and their immediate family members” unable to get commercial tickets out of the country.
Mr Kirby sought to quell concerns about Americans in Gaza, who have so far been offered no way out of the territory.
Citing an unnamed US official, The Washington Post reported that about 500 Americans are stuck in Gaza.
“Any American citizen that's in Gaza or Israel, we certainly want to hear from them and we will do everything we can to help them leave if they want to leave. Different geography, different challenges, but that doesn't mean that we aren't still committed … and that includes the West Bank,” Mr Kirby said.
The update on Israel-bound US flights comes after Mr Biden on Friday hosted a call with families of Americans missing or taken hostage by Hamas.
In a preview from a 60 Minutes interview, Mr Biden said the families “have to know the President of the United States of America cares deeply about what's happened to them”.
The President told the families the “government is doing everything possible to bring home their loved ones”, Mr Kirby added.