A decision by U.S. President Joe Biden is holding up a delivery of thousands of heavy bombs to the Israel Defense Forces was taken in the context of Jerusalem’s plans to carry out a large-scale ground offensive in Rafah, Defense Secretary Lloyd Austin told Senators on Wednesday.

“We’ve been very clear that Israel shouldn’t launch a major attack into Rafah without accounting for and protecting the civilians that are in that battlespace,” Austin said, according to a Reuters report.

“And again, as we have assessed the situation, we have paused one shipment of high payload munitions,” he said during a hearing on Biden’s 2025 defense budget request. “We’ve not made a final determination on how to proceed with that shipment.”

On Tuesday night, an unnamed Biden administration official confirmed reports that Washington had held up a munitions shipment. A senior official told CBS News that the U.S. stopped the delivery of the bombs over fears that they could be used during the operation in Rafah.

The shipment to the IDF included 1,800 bombs weighing 2,000 pounds each and another 1,700 bombs weighing 500 pounds each.

It marked the first time since the Hamas-led assault on the northwestern Negev on Oct. 7 and the ensuing war in the Gaza Strip that Washington has held up arms supplies to its Middle Eastern ally.