President Joe Biden said that he would not supply offensive weapons that Israel could use to launch an all-out assault on Rafah — the last major Hamas stronghold in Gaza — over concern for the well-being of the more than 1 million civilians sheltering there.

Biden, in an interview with CNN on Wednesday, said that the U.S. was still committed to Israel’s defense and would supply Iron Dome rocket interceptors and other defensive arms but that if Israel goes into Rafah, “we’re not going to supply the weapons and artillery shells used.”

Biden acknowledged that “civilians have been killed in Gaza” by the type of heavy bombs that the U.S. has been supplying -- his first validation of what administration critics have been loudly protesting, even if he still stopped short of taking responsibility. His threat to hold up artillery shells expanded on earlier revelations that the U.S. was going to pause a shipment of heavy bombs.

The U.S. has historically provided enormous amounts of military aid to Israel. That has only accelerated in the aftermath of Hamas’ Oct. 7 attack, which killed some 1,200 people in Israel and led to about 250 being taken captive by militants. Biden’s comments and his decision last week to pause the shipment of heavy bombs to Israel are the most striking manifestations of the growing daylight between his administration and Israel Prime Minister Benjamin Netanyahu’s government. Biden said Wednesday that Israel’s actions around Rafah had “not yet” crossed his red lines, but has repeated that Israel needs to do far more to protect the lives of civilians in Gaza.

The shipment was supposed to consist of 1,800 2,000-pound (900-kilogram) bombs and 1,700 500-pound (225-kilogram) bombs, according to a senior U.S. administration official who spoke on the condition of anonymity to discuss the sensitive matter. The focus of U.S. concern was the larger explosives and how they could be used in a dense urban area.