President Joe Biden threatened to pull support for Israel unless Prime Minister Benjamin Netanyahu accepts an “immediate ceasefire” and takes steps to curb civilian casualties in Gaza.

The demand, made in a Thursday phone call with the Israeli leader — their first since Israel Defense Forces bombed a humanitarian convoy, killing seven World Central Kitchen aid workers — marks a dramatic escalation in the president’s posture toward the Jewish state.

Biden had previously told WCK founder Chef Jose Andres that the attack left him “heartbroken” and that he would press Israel to change its military operations in Gaza. The strike, which Israel called an accident, killed one American citizen.

“President Biden emphasized that the strikes on humanitarian workers and the overall humanitarian situation are unacceptable. He made clear the need for Israel to announce and implement a series of specific, concrete, and measurable steps to address civilian harm, humanitarian suffering, and the safety of aid workers,” the White House‘s readout of the call states.

“He made clear that U.S. policy with respect to Gaza will be determined by our assessment of Israel’s immediate action on these steps,” the statement adds. “He underscored that an immediate ceasefire is essential to stabilize and improve the humanitarian situation and protect innocent civilians, and he urged the Prime Minister to empower his negotiators to conclude a deal without delay to bring the hostages home.”

National Security Council spokesman John Kirby declined to elaborate on what conditions Biden set for Israel should it not change its operating procedures regarding Gaza.

“What we are looking to see and hope to see here in the coming hours and days is a dramatic increase in humanitarian assistance getting in, additional crossings opened up, and a reduction in the violence against civilians and certainly aid workers,” he explained. “In the coming days, we will be looking for concrete, tangible steps.”

“I won’t get ahead of what the Israelis will or won’t announce,” Kirby continued. “And it’s not just about the announcement of concrete steps and changes in their policies, but it’s the execution of those announcements and those decisions and implementing them. And so, we obviously will watch closely and monitor how they do and on the commitments that they make. And as I said earlier, if there’s no changes to their policy in their approaches, then there’s going to have to be changes to ours.”

CLICK HERE TO READ MORE FROM THE WASHINGTON EXAMINER

White House officials also said Biden and Netanyahu discussed threats posed by Iran and the U.S. commitment to help Israel defend itself from those threats. The call reportedly lasted roughly half an hour.

The president has been under increasing pressure as civilian casualties in Gaza continue to mount. Biden hosted Muslim American leaders at the White House on Tuesday for a closed-door discussion on the situation in Gaza, yet White House officials declined to say if they believed the discussion was a success on Wednesday.