Defense Secretary Pete Hegseth ordered a pause on sending a shipment of missiles and ammunition to Ukraine amid concern about the U.S. military’s stockpiles.

The U.S. is halting some shipments of weapons to Ukraine amid concerns that its own stockpiles have declined too much, officials said Tuesday. The munitions were previously promised to Ukraine for use during its ongoing war with Russia under the Biden administration.

The decision was driven by the Pentagon’s policy chief, Elbridge Colby, and was made after a review of Pentagon munitions stockpiles.