MOSCOW: Russian President Vladimir Putin on Tuesday lowered the threshold for a nuclear strike in response to a broader range of conventional attacks, and Moscow said Kyiv had struck deep inside Russia with US-made ATACMS (Army Tac­tical Missile System) missiles. Putin approved the change days after two US officials and a source familiar with the decision said on Sunday that President Joe Biden’s administration had allowed Ukraine to use US-made weapons to strike deep inside Russia. Moscow had been warning the West for months that if Washington allowed Ukraine to fire US, British and French missiles deep into Russia, Moscow would consider those Nato members to be directly involved in the war in Ukraine. The updated Russian nuclear doctrine, establishing a framework for conditions under which President Putin could order a strike from the world’s biggest nuclear arsenal, was approved by him on Tuesday, according to a published decree. Under new policy, any attack on Russia by a ‘non-nuclear state’ backed by a nuclear power, will be treated as a joint attack Analysts said the biggest change was that Russia could consider a nuclear strike in response to a conventional attack on Russia or its ally Belarus that ‘created a critical threat to their sovereignty and (or) their territorial integrity’. “The big picture is that Russia is lowering the threshold for a nuclear strike in response to a possible conventional attack,” said Alexander Graef, a researcher at the Institute for Peace Research and Security Policy at the University of Hamburg, Germany. The previous doctrine, contained in a 2020 decree, said Russia may use nuclear weapons in case of a nuclear attack by an enemy or a conventional attack that threatened the existence of the state. The US National Security Council said it had not seen any reason to adjust its nuclear posture. Together, Russia and the US control 88 per cent of the world’s nuclear warheads. Vladimir Putin is the primary decision-maker on the use of Russia’s nuclear arsenal. The doctrine said any attack on Russia 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. Russia’s defence ministry said Ukraine had struck the country’s Bryansk region with six missiles on Tuesday, and that air defence systems intercepted five and damaged one. “We will be taking this as a qualitatively new phase of the Western war against Russia and we will react accordingly,” Foreign Minister Sergei Lavrov said in English, adding that US personnel and data must have been used in the ATACMS attack on Russia. Lavrov said Russia would do everything to avoid nuclear war, and pointed out that it was the US which used nuclear weapons against the Japanese cities of Hiroshima and Nagasaki in 1945. On the 1,000th day of the Ukraine war, Russia also included a broader definition of the data that could be used to indicate it was under mass attack from aircraft, cruise missiles and unpiloted aircraft.