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

The White House cited Pentagon concerns that some American arms stockpiles were dwindling too low. Among the affected weapons were air defense systems, bombs, missiles and artillery rounds.

Among the halted supplies are Patriot air defence systems, artillery rounds, and missiles used by Ukrainian forces in US-made F-16 jets, according to Pentagon officials. These systems have been instrumental in helping Ukraine resist intensified Russian attacks over the past few months.