President Donald Trump complained Thursday that the United States provided too many weapons to Ukraine under the previous administration, his first public comments on the pause in some shipments as Russia escalates its latest offensive.

The U.S. move affects high-demand munitions, including Patriot missiles, the AIM-7 Sparrow air-to-air missile and shorter-range Stinger missiles.

Analysts say Ukraine’s European allies can fill some of the gaps and provide artillery systems. But they don’t possess alternatives to the U.S.-made HIMARS missiles and air defense systems, especially Patriots, which are crucial to help defend Ukrainian cities.