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 has been pleading with the US for months to let it use American-made weapons to hit military targets inside Russia beyond the border zone. Now, as he nears the end of his presidency, Joe Biden has relented and decided to lift some restrictions,

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