The White House last week paused a shipment of weapons to Israel, as Israeli leaders closed in on a decision to launch an operation in the southern Gaza city of Rafah, a senior administration official said Tuesday. 

Defense Secretary Lloyd Austin confirmed Wednesday in testimony to Congress that “we paused one shipment of high payload munitions.”

Meanwhile, Israel’s military announced Tuesday the launch of “targeted strikes” against Hamas in Rafah, which Israel has said is Hamas’ last stronghold, after Israel’s War Cabinet approved a military operation in the city. 

The U.S. has long held that Israel shouldn’t launch such a major ground operation in Rafah, where more than 1 million people are taking shelter after fleeing other parts of Gaza. But the United States’ concerns in discussions with Israel about addressing humanitarian needs in Rafah and how to approach Hamas have not been sufficiently addressed, the senior administration official said. When Israeli leaders appeared close to a decision on Rafah, the Biden administration began to review upcoming transfers of weapons that could be used in Rafah, and as a result, paused one shipment last week, the official said. 

That stalled shipment contains 1,800 2,000-pound bombs and 1,700 500-pound bombs, the former of which the Biden administration was particularly concerned could do severe damage in urban areas, the official said. The senior administration official said the U.S. hasn’t yet decided how to proceed on this particular shipment. 

News of the weapons pause comes after days of the administration downplaying the possibility that it delayed a shipment. 

Israeli tanks on Tuesday took control of the Gaza side of the Rafah border near Egypt, as Israel’s operation continues. That means Gaza’s two key aid corridors are shut. 

The senior administration official said the paused shipment has nothing to do with the funding for Israel Congress passed last month. 

Israel has long been threatening a ground assault on Rafah, and confirmed the beginning of the Rafah operation after Israel said a cease-fire proposal Hamas agreed to is “far from meeting Israel’s core demands.” 

Cease-fire talks are continuing in the Middle East and CIA director Bill Burns is in Israel Wednesday for talks with Prime Minister Benjamin Netanyahu. 

The United States’ decision to pause the weapons shipment — and a senior administration official’s willingness to share the reasoning for the pause — point to the Biden administration’s growing concern over how Israel’s actions are harming Palestinian civilians.