WASHINGTON (AP) — The United States warned on Thursday that Israel will be dealing a strategic victory to Hamas if it carries out plans for an all-out assault on Rafah, the militants’ last major stronghold in Gaza.

The warning was backed by a new threat from President Joe Biden: He says he will pause more offensive military assistance to Israel if it goes through with the operation in a city where more than 1 million civilians are sheltering.

Biden last week put on hold a shipment of large bombs to Israel over concerns the weapons are of the type that has caused significant civilian casualties in Gaza and would almost certainly do more such damage if Israel conducted a major offensive in Rafah.

On Wednesday, he held out the possibility of holding up future shipments of bomb guidance kits and artillery to Israel, in hopes the threat would turn Israel back from an operation in the city.