President Biden threatened on Thursday to condition future support for Israel on how it addresses his concerns about civilian casualties and the humanitarian crisis in Gaza, attempting for the first time to leverage American aid to influence the conduct of the war against Hamas.

During an evidently tense 30-minute call with Prime Minister Benjamin Netanyahu of Israel, Mr. Biden went further than ever before in pressing for change in the military operation that has inflamed many Americans and others around the world. But the White House stopped short of directly saying the president would halt arms supplies or impose conditions for their use, as fellow Democrats have urged him to do.

“President Biden emphasized that the strikes on humanitarian workers and the overall humanitarian situation are unacceptable,” the White House said in a statement. “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. 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 was the sharpest issued by the White House in the six months of Israel’s war against Hamas, underscoring the president’s growing frustration with Mr. Netanyahu, who has defied American pressure to do more to reduce the suffering of civilians in Gaza. Mr. Biden, who has staunchly expressed support for Israel’s right to respond to the Oct. 7 Hamas terrorist attack, lashed out over this week’s killing of seven aid workers by Israeli military forces.

A group inspecting damages after an airstrike in Rafah, the southern Gaza city, on Thursday.Credit…Fatima Shbair/Associated Press

John F. Kirby, a White House spokesman, said the president wants to see “concrete tangible steps” to reduce the violence against civilians and increase access for humanitarian aid to Gaza. He said the White House expects Israel to make announcements of specific changes within hours or days.

But Mr. Kirby would not outline specific metrics for judging Israel’s response or what Mr. Biden would do if not satisfied. “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,” he said.

The president has long resisted curbing the arms flow to Israel to influence its conduct of the war, with aides arguing that many of the munitions sent are air defense missiles. But even some of Mr. Biden’s close Democratic allies have increasingly come around to the view that Washington should exercise more control over the weaponry, including Senator Chris Coons, a fellow Democrat from Delaware and confidant of the president.

“I think we’re at that point,” Mr. Coons said on CNN on Thursday morning, adding that if Mr. Netanyahu were to order the Israeli military into the southern Gaza city of Rafah in force and “drop thousand-pound bombs and send in a battalion to go after Hamas and make no provision for civilians or for humanitarian aid, that I would vote to condition aid to Israel.”

Mr. Netanyahu did not immediately release a description of the call, but in other comments on Thursday appeared unbowed. In a meeting in Jerusalem with visiting Republican lawmakers organized by the American Israel Public Affairs Committee, known as AIPAC, the prime minister pushed back strongly against Mr. Biden’s insistence on a two-state solution to the Palestinian conflict.

“There is a contrary move, an attempt to force, ram down our throats a Palestinian state, which will be another terror haven, another launching ground for an attempt, as was the Hamas state in Gaza,” Mr. Netanyahu said. “That is opposed by Israelis, overwhelmingly.”

In a separate video statement, he focused on the threat he sees from Iran. “For years Iran has been acting against us, both directly and though its proxies, and therefore Israel is acting against Iran and its proxies, in both defensive and offensive operations,” he said, referring to an Israeli airstrike that killed seven Iranian military officers in Syria this week.

“We will know how to defend ourselves,” he added, “and we will operate according to the simple principle by which those who attack us or plan to attack us — we will attack them.”

The White House said that Mr. Biden stood by Israel against Iran during his Thursday call with Mr. Netanyahu, which Vice President Kamala Harris, Secretary of State Antony J. Blinken and Jake Sullivan, the national security adviser, joined in.

“The two leaders also discussed public Iranian threats against Israel and the Israeli people,” the White House statement said. “President Biden made clear that the United States strongly supports Israel in the face of those threats.”

The president’s threat to condition American support on Israeli conduct came under rising pressure from his own party. Some of former President Barack Obama’s old team have grown more outspoken in castigating Mr. Biden for not doing more to restrain Mr. Netanyahu, who goes by the nickname Bibi, and the Israel Defense Forces, or I.D.F., saying that the president’s expressed outrage was meaningless otherwise.

Inspecting on Tuesday one of the vehicles used by World Central Kitchen workers destroyed in strikes by Israeli forces. Credit…Mohammed Saber/EPA, via Shutterstock

“The U.S. government is still supplying 2 thousand pound bombs and ammunition to support Israel’s policy,” Ben Rhodes, a former deputy national security adviser to Mr. Obama, wrote on social media. “Until there are substantive consequences, this outrage does nothing. Bibi obviously doesn’t care what the U.S. says, its about what the U.S. does.”

Jon Favreau, a former chief speechwriter for Mr. Obama, was even more derisive of Mr. Biden. “The president doesn’t get credit for being ‘privately enraged’ when he still refuses to use leverage to stop the IDF from killing and starving innocent people,” he wrote. “These stories only make him look weak.”

The killing of the World Central Kitchen workers has inflamed the tensions between Washington and Jerusalem at a time when Mr. Biden has complained that Israel has not done enough to curb the killings of civilians or facilitate the provision of humanitarian aid into Gaza. Mr. Biden called himself “outraged and heartbroken” over the incident and made a point of calling José Andrés, the celebrity chef who founded World Central Kitchen, to express his condolences.




Inside World Central Kitchen’s Work in Gaza

World Central Kitchen has suspended its relief efforts in Gaza after seven aid workers were killed in Israeli airstrikes on Monday. Videos reveal the challenges of food distribution in a territory under siege.

Zomi Frankcom and Damian Soból arrived in Gaza on a mission to feed Palestinians, documenting their efforts in social media videos like these. Then on April 1, they were killed by Israeli airstrikes, along with five other colleagues, bringing the work of the World Central Kitchen in Gaza to a halt. The charity’s videos offer a rare window into the challenges of food distribution in Gaza, a territory on the brink of famine that’s been cut off from the outside world. Celebrity chef José Andrés started World Central Kitchen in 2010 in response to the earthquake in Haiti. The organization brings meals to areas impacted by natural disasters or conflict, including communities displaced inside Israel after the Oct. 7 attacks. Since October, the group said it delivered more than 43 million meals to Palestinians through community kitchens, truck convoys and airdrops. In mid-March, they were the first to deliver aid by sea with a ship carrying nearly 200 tons of food from Cyprus. The Israeli military released footage of the coordination behind that effort, which brought food to northern Gaza, where the U.N. says people are facing catastrophic levels of hunger. “I’m very hopeful that we can be bringing millions and millions of meals daily. We may fail, but the biggest failure will be not trying.” A second maritime delivery arrived just hours before the attack. In a video statement, the Israeli military called the attack a grave mistake. Since Oct. 7, nearly 200 aid workers have been killed in Gaza, according to the U.N. And for now, the World Central Kitchen has suspended its operations there.

World Central Kitchen has suspended its relief efforts in Gaza after seven aid workers were killed in Israeli airstrikes on Monday. Videos reveal the challenges of food distribution in a territory under siege.

The seven were killed by three successive strikes on three cars traveling along a road in Gaza. Israeli officials have called the episode a tragic mistake based on a misidentification of the vehicles, but have not explained more explicitly how it happened. The cars were marked with World Central Kitchen logos, although the attack took place at night. Mr. Andrés has said his organization kept in touch with Israeli officials about travel plans.

As of Thursday morning, the Israelis had not yet communicated any initial findings of their promised investigation into the strike to the United States, according to a senior Biden administration official who spoke on the condition of anonymity to detail internal conversations.

Some Palestinian advocates reacted with aggravation to Mr. Biden’s expression of outrage over the deaths of the aid workers because in their view he has not responded with nearly enough indignation over the killing of more than 30,000 people living in Gaza, most of them civilians.

The president is evidently coming under pressure even from within his own family. Mr. Biden told Muslim community leaders at the White House on Tuesday evening that the first lady, Jill Biden had weighed in, telling him, “Stop it, stop it now, Joe.”

Katie Rogers contributed reporting.