With an invasion of southern Gaza's Rafah looking more likely, the U.S. paused last week a shipment of bombs to Israel, an official in Washington said Tuesday.
The decision marks the first time in the ongoing conflict that President Joe Biden has squeezed military aid to the key U.S. ally.
Washington halted a load of some 1,800 2,000-pound (907 kilograms) bombs and 1,700 500-pound (226 kilograms) bombs after Israel had not "fully addressed" U.S. concerns about a major ground operation, a senior administration official said.
News of the move comes as the White House blasted the "unacceptable" closure of the Rafah border crossing with Egypt after Israel sent tanks in earlier Tuesday – while holding out hope for a cease-fire with Hamas.
The pausing of weapons marks the first time that Biden has acted on the warning that he gave Prime Minister Benjamin Netanyahu in April that U.S. policy on Gaza would depend on how Israel treated civilians.
The U.S. official said Biden's administration decided on the weapons when it appeared Israel was on the verge of a major ground operation into Rafah, which Washington has strongly opposed as more than a million people are sheltering there.
Israeli and U.S. officials had been discussing alternatives but "those discussions are ongoing and have not fully addressed our concerns," the senior U.S. official said, speaking on condition of anonymity.
"As Israeli leaders seemed to approach a decision point on such an operation, we began to carefully review proposed transfers of particular weapons to Israel that might be used in Rafah. This began in April."
The U.S. official said Washington was "especially focused" on the use of the heaviest 900-kilogram bombs "and the impact they could have in dense urban settings as we have seen in other parts of Gaza."
"We have not made a final determination on how to proceed with this shipment," the official said.
The U.S. State Department is still reviewing other weapons transfers, including the use of precision bomb kits known as JDAMs, added the official.
The White House said earlier that Israel had promised the military thrust into Rafah earlier Tuesday was a "limited operation" and not the feared full-scale invasion.
'Absurd demands'
While facing a difficult reelection battle in November against Republican rival Donald Trump, Biden has come under growing domestic pressure over his support for Israel, with widespread protests at U.S. universities leading to police crackdowns and thousands of arrests.
Republicans have also piled on the political pressure, and U.S. House Speaker Mike Johnson – who has repeatedly claimed the protests are anti-Semitic – criticized Tuesday any move to limit military aid.
"Just when we thought it was only university presidents who are caving into the absurd demands of the pro-Hamas students, the president himself has now reportedly halted ammunition shipments to Israel," Johnson said to reporters ahead of the official U.S. announcement.
Johnson said it was "undermining" a huge aid package with military support for Israel and Ukraine that Congress passed after months of delays in April – although the U.S. official said the halted shipment was not linked to that package.
Biden's move does, however, turn the screw on Israel to end the seven-month conflict and to take more action on the humanitarian situation in Gaza.
"The crossings that have been closed need to be reopened, it is unacceptable for them to be closed," White House Press Secretary Karine Jean-Pierre told a briefing earlier Tuesday over Israel's seizure of the Rafah crossing.
The war was triggered by the Oct. 7 Hamas incursion of southern Israel, which resulted in the deaths of more than 1,170 people, according to an AFP tally of Israeli official figures.
Israel's brutal retaliatory offensive, in comparison, killed at least 34,789 people in Gaza, mostly women and children, according to the territory's Health Ministry.