The decision left officials on both sides of the Atlantic scrambling to find out how long the pause might last.

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.

Ukraine is forging ahead with early plans for joint weapons production with some international allies, top officials said, while warning yesterday of potential consequences of the US decision to halt some arms shipments promised to help Kyiv fight off Russia’s invasion.