NEW: Ukraine fires U.S. provided long-range missiles into Russia just days after ...

NEW: Ukraine fires U.S. provided long-range missiles into Russia just days after President Biden gave Ukraine the green light.

The move comes just two months after Putin said that if Ukraine used these missiles to strike Russia, it would mean the U.S. is at war.

Putin in September: If Ukraine uses U.S. long-range missiles to strike Russia, the "United States is at war with Russia."