The decision to change Russia's official nuclear doctrine is the Kremlin's answer to a reported decision by the administration of U.S. President Joe Biden to allow Ukraine to fire American long-range missiles deep into Russia.

Russian President Vladimir Putin signed on Tuesday a revised nuclear doctrine that lowers the threshhold for the use of weapons. The publication of the document on the Kremlin website on Tuesday coincided with the 1000th day of Russia's full-scale invasion of Ukraine.

Russian 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.