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

The move "was made to put America’s interests first," a White House spokeswoman said, as U.S. munitions have been depleted in recent years.

Lawmakers, former diplomats and experts questioned the Trump administration’s decision to halt the supply of some air-defense weapons to Ukraine, saying the move risks prolonging the war with Russia and leaving the country more vulnerable to stepped-up missile and drone barrages.