Russia has changed its nuclear doctrine in response to the U.S. decision to allow Ukraine to fire American-made ballistic missiles deeper into Russia.

Ukraine used U.S. ATACMS missiles to strike Russian territory on Tuesday, taking advantage of newly granted permission from the outgoing Biden administration on the war's 1,000th day. Russia said its forces shot down five of six of the missiles,

The Biden administration has allowed Ukraine to use Army Tactical Missiles Systems, a long-range missile system that often carries cluster bombs.