The Biden administration paused the shipment of thousands of weapons to Israel, including controversial 2,000-pound bombs, amid mounting concern about the country’s plan to expand a military operation in southern Gaza that could dramatically increase the conflict’s death toll, U.S. officials said Tuesday.

“Israel should not launch a major ground operation in Rafah, where more than a million people are sheltering with nowhere else to go,” said a senior administration official, explaining the U.S. decision to pause the weapons shipments. “We are especially focused on the end-use of the 2,000-pound bombs and the impact they could have in dense urban settings as we have seen in other parts of Gaza.”