Speaking to a congressional committee, Defense Secretary Lloyd Austin confirmed the freeze last week on 1,800 2,000-lb (907 kg) bombs and 1,700 500-lb (226 kg) bombs.

"We paused one shipment of high-payload munitions" for Israel but have not "made a final determination on how to proceed with that shipment," Austin said.

State Department spokesman Matthew Miller said the United States had "very serious concerns" about Israel's stated plans to go into Rafah, where more than one million Palestinians have taken shelter during the war.

"So we have paused one shipment of near-term assistance and we are reviewing others," Miller said.

But he said that the United States still had a "long-term commitment" to Israel's security and pointed to US assistance last month in shooting down drones fired from Iran.

"People should be absolutely clear that we are committed to Israel's security," he said.

But in Rafah, Miller said, "there are so many people crammed into such a small area."

He said that the United States was looking "at the way Israel has conducted its operations in the past and what the impact on civilian population has been."

Israeli Prime Minister Benjamin Netanyahu has vowed to go into Rafah as part of the campaign to eliminate Hamas after the militants' attack inside Israel on October 7.