Russia’s nuclear doctrine now sees any aggression made with the help of a nuclear state as a joint attack.
President Vladimir Putin approved an update to Russia’s nuclear doctrine, widening the scenarios in which it would consider a strike.
The move seemed a direct response to events in Ukraine, where the US recently allowed Kyiv to use American weapons for longer-range attacks on Russia.
The changes, first mooted in September, were approved on Tuesday.
They build on a series of nuclear threats Putin has issued since the beginning of the full-scale war in Ukraine, though none have come to pass.
Western powers consider the use of nukes a disaster scenario that could escalate a now-regional war into a global conflict.
In the new doctrine, Russia said that attacks from a non-nuclear state could be considered as serious as those from a nuclear-armed one, if the nuclear states are helping.
That matches the situation being considered by Ukraine, which is receiving weaponry and intelligence support from Western allies including the US and has long wished to strike Russia with their weapons.
