Maxim Shipenkov/The Associated Press
 
KYIV, Ukraine
 

President Vladimir Putin on Tuesday signed a revised nuclear doctrine declaring that a conventional attack on Russia by any nation that is supported by a nuclear power will be considered a joint attack on his country.
 

Putin’s endorsement of the new nuclear deterrent policy comes on the 1,000th day after he sent troops into Ukraine, on Feb. 24, 2022.
 

It follows U.S. President Joe Biden’s decision to let Ukraine strike targets inside Russia with U.S.-supplied longer-range missiles.
 
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