Stockpiles at risk include long-range Precision Strike Missiles and Army Tactical Missile Systems, as well as short-range Stinger surface-to-air missiles, other officials said. The U.S. had previously assessed that Putin wouldn’t provoke a North Atlantic Treaty Organization country while he is still fighting in Ukraine. But that assessment changed earlier this year, the U.S. officials said, as Putin is squeezed in Ukraine and under pressure at home to secure a victory. U.S. and European leaders increasingly see signs of Russia conducting probing attacks to test NATO’s resolve, including Russian cruise missiles that have landed in Poland and drones flown into Romania . The concern is that Putin may become more dangerous when backed into a corner, the U.S. officials said.