President Joe Biden told Prime Minister Benjamin Netanyahu on Thursday that continued American support for the war in Gaza depends on Israeli measures to protect civilians, in the clearest indication of the possibility of restricting military aid after nearly seven months of war with Hamas.

The US President urged the Israeli Prime Minister to reach an “immediate ceasefire,” in their first phone call since the killing of seven humanitarian workers, most of them foreigners, in an Israeli air strike in the besieged Gaza Strip, whose population is threatened by famine.

The United States is the most prominent political and military supporter of the Hebrew state since the outbreak of war with the Islamic Resistance Movement (Hamas) on October 7. However, some discrepancies between the two allies have begun to appear publicly in recent weeks, with increasing pressure on Democrat Biden to do more to put an end to the war that has claimed thousands of victims and caused a severe humanitarian crisis.

In a phone call with Netanyahu, Biden called for “announcing and implementing a series of specific, concrete, and measurable steps to address civilian harm, human suffering, and the safety of aid workers,” according to a White House statement.

He added that Biden “made clear that US policy regarding Gaza will be determined by our assessment of the immediate action that Israel will take regarding these steps.”

In statements to reporters, US National Security Council spokesman John Kirby confirmed that “our support for Israel’s self-defense remains firm,” adding that the Hebrew state faces “a range of threats, and the United States will not abandon them.”

But Kirby acknowledged “growing frustration” with the Israeli prime minister. “Yes, there is growing frustration,” he said in response to a question about whether the phone call reflected Biden’s frustration with Netanyahu’s failure to respond to Washington’s requests.

However, he stressed that the Biden administration wants Israel to take measures to improve humanitarian conditions in the Strip, where more than two million people face the risk of famine.

“What we are looking forward to seeing and hope to see here in the coming hours and days is a massive increase in humanitarian access, the opening of additional crossings, and a reduction in violence against civilians and aid workers,” Kirby said.

- Ceasefire and hostage release -

On Wednesday, Biden criticized Israel for the aerial bombardment that killed seven relief workers, stressing that it “did not do enough” to protect volunteers who provide a helping hand to Palestinians who are “starving.”

Biden said in a strongly worded statement that he felt “anger and sadness” over the killing of seven members of the US-based non-governmental organization World Central Kitchen.

The Israeli army acknowledged that they were killed in an accidental air strike.

In their call on Thursday, the US President told Netanyahu that the raids on relief workers, as well as the humanitarian situation in Gaza, were “unacceptable.”

The statement said that Biden “stressed that an immediate ceasefire is necessary to achieve stability, improve the humanitarian situation and protect innocent civilians, and urged the Prime Minister to enable his negotiators to reach an agreement without delay to return the hostages.”

The United States supports a ceasefire as part of an exchange deal that it hopes will eventually lead to a long-term settlement.

Biden has expressed growing frustration with Netanyahu for months, but he also strongly defended Israel's right to respond to Hamas after its unprecedented attack on Israel on October 7.

Despite pressure from the left wing of the Democratic Party to which Biden belongs, the administration continues to provide military supplies to Israel even while criticizing the way the war is being fought.

The American newspaper “The Washington Post” reported Thursday that the Biden administration agreed to supply Israel with thousands of bombs, on the same day of the bombing that killed members of the “Global Central Kitchen.”