Israeli Prime Minister Benjamin Netanyahu vowed to invade Rafah on Tuesday as negotiations between Israel and Hamas on a ceasefire deal continue.

The United States and Israel disagree about the potential of an Israeli military ground invasion into Rafah, the southernmost city of Gaza along the Egyptian border where more than a million Palestinians have sought refuge during the war. It is also Hamas’s last remaining stronghold. Several governments, the U.S. included, and international entities have warned there could be significant civilian casualties if Israel goes ahead with full-scale military operations in the city without proper and extensive planning.