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

The call between Trump and Putin comes just one day after Washington indirectly aided Putin’s war effort against Ukraine by suspending some shipments of air defense missiles, artillery shells and other weapons as part of what Pentagon officials have described as a pause of arms shipments globally while the U.S. replenishes its own stockpiles.

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.