Russian President Vladimir Putin has approved changes to Russia's nuclear doctrine, setting new conditions under which the country would consider using its arsenal.
It is envisaged that in the event of an attack by a non-nuclear state, which is backed by a nuclear power, it will be treated as a joint attack on Russia.
The change was proposed in September and was signed only today, when it was 1000 days since the start of the war.
This decision comes after the permission that Washington gave to Kiev for the use of American long-range weapons against Russia.
Under the amendments, a major attack on Russia by 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 that is a member of a coalition would be seen by Moscow as aggression by the entire group.
The changes expand the number of countries and coalitions, and the types of military threats, that are subject to a possible nuclear response, according to the state news agency Tass.
On Monday, Russia warned of an appropriate and tangible response to US President Joe Biden's move to allow Ukraine to 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.
Peskov said Tuesday that the new doctrine was released "at the right time" and that Putin had asked for it to be updated earlier this year to be "in line with the current situation," AP reported.