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(WASHINGTON) — The Biden administration is delaying shipments of ammunition expected to be sent to Israel, three U.S. officials told ABC News on Tuesday in what appears to be the first time since the Oct. 7 Hamas attacks that the U.S. has withheld weapons from its ally.

According to one U.S. official, the U.S. Air Force has been told by the White House National Security Council to pause shipments of ammunition that were already approved and under contract, waiting to be shipped from Dover Air Force Base.

A second U.S. official confirmed to ABC News that the NSC was behind the decision to pause the munitions. U.S. officials said the delay has affected more than one delivery and is being done intentionally.

The NSC has not confirmed the decision or said why the shipments were put on hold.

“Our commitment to Israel’s security remains ironclad,” said White House spokesman John Kirby. “We don’t as a matter of course talk about individual shipments one way or the other. But again, nothing’s changed about our commitment to Israel security.”

The move comes as the Biden administration has tried to increase pressure on Israel not to launch a full-scale invasion of Rafah in southern Gaza without a plan to protect the million civilians seeking refuge there. On Tuesday, Israel began what its officials called a “precise” operation in Rafah.

While Biden has faced demands from some Democrats that he put conditions on further arms transfers to Israel, Republicans were quick to criticize the move.

House Speaker Mike Johnson on Tuesday said he received a report from on the ground in Israel that said “a shipload of munitions and precision weapons, which are to be used to help protect civilians and Rafah, is being withheld.”

In a letter to Biden, Republican Sens. Jodi Ernst and Ted Budd said they were “shocked” and “deeply concerned” that the Biden administration failed to notify Congress before withholding ammunition to Israel.

“If these reports are true, then you have once again broken your promise to an American ally,” they said.

Israeli Prime Minister Benjamin Netanyahu has said operations in Rafah are inevitable and necessary to eliminate Hamas.

Axios first reported on Sunday that a shipment of ammunition from the U.S. to Israel had been held up.

Defense Secretary Lloyd Austin is expected to testify Wednesday before a Senate panel, where he will likely be asked about U.S. policy.

ABC News’ Lauren Peller and Molly Nagle contributed to this report.

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