Putin is the primary decision-maker on the use of Russia's nuclear arsenal. The doctrine said any attack by a non-nuclear power supported by a nuclear power would be considered a joint attack, and that any attack by one member of a military bloc would be considered an attack by the entire alliance, it said.

President Vladimir Putin said on Thursday that the Ukraine war was escalating towards a global conflict after the United States and Britain allowed Ukraine to hit Russia with their weapons, and warned the West that Moscow could strike back.

Vladimir Putin could face a revolt within his own country if he were to launch an attack on the United States or the United Kingdom. This week saw a fresh escalation in tensions, with Washington and London authorizing Ukraine to use their long-range missiles on Russian territory.

This week's saber rattling has come during a period in which the war has passed 1,000 days and at a pivotal moment in the conflict between Moscow and Kyiv.