MOSCOW, Nov 19 (BBC): Vladimir Putin has approved changes to Russia's nuclear doctrine, setting out new conditions under which the country would consider using its arsenal.
The doctrine now says an attack from a non-nuclear state, if backed by a nuclear power, will be treated as a joint assault on Russia.
The update was proposed in September and rubber stamped on Tuesday, the 1,000th day of the war with Ukraine.
It also follows Washington's decision on Monday to allow Ukraine to fire long-range US missiles into Russia.
Under the changes, a large attack on Russia with conventional missiles, drones or aircraft could meet the criteria for a nuclear response, as could an attack on Belarus or any critical threat to Russia's sovereignty.
Any aggression against Russia by a state which is a member of a coalition would be seen by Moscow as aggression from the whole group.
The updates expand the number of countries and coalitions, and the kinds of military threats, subject to a possible nuclear response, according to state-run news agency Tass.
Putin has threatened the use of nuclear weapons before, and Ukraine has criticised it as "nuclear sabre-rattling" to deter its allies from providing further support.
Missile news welcomed in Ukraine but 'won't win war'
Announcing the change, the Kremlin urged other countries to study the changes.
"This is a very important text," Kremlin spokesperson Dmitry Peskov said, according to Tass, adding "it should become a subject to a very deep analysis".
On Monday, Russia warned of "an appropriate and tangible" response to US President Joe Biden's move to let Ukraine use ATACMS missiles to strike the country.
Such an attack inside Russian territory "would represent the direct involvement of the United States and its satellites in hostilities against Russia", a foreign ministry statement said.
Mr Peskov said on Tuesday that the new doctrine was published "in a timely manner" and that Putin had requested it be updated earlier this year so that it was "in line with the current situation", AP reported.
Russia says the use of US long-range missiles by Ukraine will lead to "an appropriate and tangible" response.
Such an attack inside Russian territory "would represent the direct involvement of the United States and its satellites in hostilities against Russia", a foreign ministry statement said.
President Joe Biden approved the use of the missiles on targets in Russia in a major change of US policy - two months before he is due to leave the White House.
It is not clear if his successor, President-elect Donald Trump, was consulted or whether he will stick by the decision, having promised to end the Russia-Ukraine war.
Ukraine has had US ATACMS (Army Tactical Missile System) with a range of 300km (190 miles) - as well as French and British Storm Shadow missiles of a similar range - but the Western allies had barred Kyiv from hitting Russia with them.
Biden's decision to lift that condition is a significant moment in the war, which marks its 1,000th day on Tuesday.
Russia launched a full-scale invasion of Ukraine on 24 February 2022.
