President Biden is signaling that growing frustration with Israeli Prime Minister Benjamin Netanyahu could lead to a change in U.S. support for Israel’s war against Hamas in the Gaza Strip, following the shocking Israeli strike killing World Central Kitchen aid workers.

The White House sharpened its message toward Israel significantly following a call between Biden and Netanyahu after months of defending Israel’s conduct, even as Palestinian civilian deaths in Gaza mounted.

The president called the strike that killed World Central Kitchen workers, who were helping to distribute food to Palestinians in Gaza, “unacceptable” during a 30-minute call with Netanyahu that officials described as “very direct.”

“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 said in a readout of the call. “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 language was a dramatic shift from just days ago, when White House national security communications adviser John Kirby dismissed the idea that the U.S. would “hang some sort of condition over their neck” when it came to providing military aid to Israel.

Kirby told reporters on Thursday the Biden-Netanyahu call was arranged after the death of the World Central Kitchen workers, which he said had left Biden “shaken.”

“I’m not going to preview any potential policy decisions coming forward,” Kirby said. “What we want to see are some real changes on the Israeli side, and, you know, if we don’t see changes from their side, there will have to be changes from our side.”

Kirby said the U.S. hoped to see in the coming “hours and days” a “dramatic increase in the humanitarian assistance getting in, additional crossings opened up, and a reduction in the violence against civilians and certainly aid workers.”

Asked whether there had been growing frustration on Biden’s part that his previous messages to Netanyahu had not gotten through, Kirby said there was.

Vice President Harris, who was on the call between Biden and Netanyahu, told Spectrum News during a trip to North Carolina that the administration has made clear it will ensure Israel “is never left without an ability to defend itself. 

“At the same time, if there are not changes to their approach, it is very likely we’re going to change our approach,” she added.

Tensions between Biden and Netanyahu have been simmering for months as the president faces a growing outcry from activists and some Democratic lawmakers over the humanitarian crisis unfolding in Gaza. Thousands of voters in Democratic primaries have cast ballots for “uncommitted” or cast a protest vote over Biden’s handling of the war.

Biden has argued the Israelis have a right to defend themselves from Hamas while simultaneously pushing for Netanyahu to do more to protect civilians. In an interview last month with MSNBC, Biden said Netanyahu was “hurting Israel more than helping” with his handling of the conflict.

The president’s call with Netanyahu came the same day Secretary of State Antony Blinken suggested to reporters that U.S. policy on Israel related to Gaza could change if calls to protect civilians are not heeded. 

And Defense Secretary Lloyd Austin in a call with his counterpart, Israeli Minister of Defense Yoav Gallant, the day before expressed his outrage at the Israeli strike that killed the World Central Kitchen aid workers.

The U.S. has also urged for a swift and immediate investigation into the strike as it continues to express increased concerns over a major operation in Rafah.

Biden’s shift in tone Thursday drew criticism from Republicans, who accused the president of caving to political pressure and threatening to abandon a key ally in Israel.

“By calling for an immediate ceasefire, the Biden admin is asking Israel to surrender to Iran- backed Hamas,” Sen. Joni Ernst (R-Iowa) wrote on X, formerly known as Twitter. “Biden is turning his back on our greatest ally in the Middle East and prioritizing the far left over American hostages held by Hamas.”

“President Biden’s message is clear: For terrorists like Hamas who kill indiscriminately and cower behind civilians — consequences are short-lived,” Raj Aryal, a spokesperson for Speaker Mike Johnson (R-La.), wrote on X.

Kirby on Thursday told reporters Israel is a “friend and a partner,” and he noted Biden has for his entire political career advocated for Israel and its longevity.

“And that’s not going to change,” Kirby added.

Biden on the call also “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.”

The Israeli leader is viewed as an obstacle to reaching a deal with Hamas for a proposal for a six-week pause in fighting, though White House officials had in the past blamed Hamas for holding up a cease-fire agreement.

The language seemed to cause confusion whether the White House would accept a pause in fighting that did not include the release of hostages.

“I can’t really improve upon the president’s language. We want to see a pause in the fighting, we want to see a cease-fire immediately, so that we can get more humanitarian assistance in and create a sense of conditions where aid organizations feel better about operating inside Gaza,” Kirby said.  

“We also, of course, as we’ve said many times, think that could also provide a window here to get the hostages out,” he added.

Laura Kelly contributed.

Updated at 6:02 p.m.