President Joe Biden warned Israel of a sharp shift in his policy over the Gaza war Thursday amid growing frustration with Benjamin Netanyahu and mounting domestic pressure in a US election year.
Biden has stood solidly behind Israel since Hamas's October 7 attacks, and until now his criticism of civilian deaths in Gaza had not stopped Washington supplying military hardware to its key ally.
But the Democrat faces spiraling anger from Muslim and younger voters over his support for Israel, and political allies at home have been pressing him to make the aid conditional on changed Israeli behavior.
In a tense 30-minute call with Netanyahu after Israeli strikes killed seven aid workers in Gaza, Biden hinted at doing just that.
For the first time, Biden "made clear that US policy with respect to Gaza will be determined by our assessment of Israel's immediate action" to end the killings and the dire humanitarian situation, the White House said.
The tough language, describing the aid worker attack as "unacceptable" and urging Israel to take steps towards an immediate ceasefire, reflected the mounting tensions with Netanyahu.
"Yes, there's been growing frustration," White House National Security Council spokesman John Kirby said.
Kirby would not confirm that halting military aid was on the table but gave Israel little room for maneuver, warning that the United States wanted to see action within the "coming hours and days".
The Biden administration faces a difficult balancing act, as it tries to calibrate its Gaza policy between what Kirby called its overall "ironclad" commitment to Israel, and mounting opposition at home to the war.
Democrats fear that anger among Arab American and Muslim voters could harm Biden in key swing states such as Michigan, which he needs to win in an expected tight election against Republican Donald Trump in November.
A key Biden confidant had earlier urged him to use the leverage afforded by the huge military aid that Washington gives Israel every year.
"I think we're at that point," Chris Coons, a Democratic senator from the president's home state of Delaware, told CNN.
Biden also reportedly faces pressure even closer to home -- from First Lady Jill Biden.
"Stop it, stop it now," she told the president about the growing toll of civilian casualties in Gaza, according to comments by Biden himself to a guest during a meeting with members of the Muslim community at the White House, and reported by The New York Times.
A Palestinian-American doctor walked out of the meeting, while several members of the Muslim community refused to take part in a traditional Ramadan fast-breaking dinner at a time when famine stalks Gaza.
Despite historic tensions with right-winger Netanyahu, Biden traveled to Israel as a self-described "Zionist" days after the Hamas attacks and hugged the premier.
But Biden's rhetoric has sharpened in recent months as the civilian death toll has soared past 30,000 and the humanitarian situation becomes ever more dire.
Biden ordered US airdrops of aid into Gaza. He also refrained from using the usual US veto at the UN Security Council, allowing a resolution calling for a ceasefire to go through -- infuriating Netanyahu.
Biden's words have, however, not been matched by any concrete steps to limit the billions of dollars in military aid that Washington supplies to its bedrock regional ally.
In a sign of business as usual, Biden's administration approved the transfer of thousands more bombs to Israel on the same day as the Israeli strikes that killed the seven aid workers, The Washington Post reported on Thursday.
Ben Rhodes, a former deputy national security advisor to president Barack Obama, called for Biden to act.
"Until there are substantive consequences, this outrage does nothing. Bibi (Netanyahu) obviously doesn't care what the US says, it's about what the US does," Rhodes said on X.
US voters are also increasingly turning against Israel's Gaza offensive.
A majority of 55 percent now disapprove of Israel's actions, compared to 36 percent who approve, according to a Gallup poll released on March 27.