In a clear message to the US and other Western powers, Russian President Vladimir Putin on Tuesday approved revisions to his nuclear doctrine amid the ongoing conflict with Ukraine. The new policy expands the scope of when Moscow can use nuclear weapons.

“It was necessary to bring our principles into line with the current situation,” Kremlin spokesman Dmitry Peskov said of the changes to Russia’s nuclear doctrine, calling the update a “very important” document that should be “studied” abroad .

Russia’s announcement coincided with the US granting Ukraine limited permission to use long-range missiles aimed at Russian territory, particularly after Putin warned the West against facilitating Kiev’s attack on Moscow.

What Putin’s updated nuclear doctrine says

According to the updated nuclear policy, Russia will consider aggression by a non-nuclear state, especially when supported by a nuclear-powered state, as a coordinated attack against it and will retaliate in kind, Reuters news agency reported.

The updated policy also allows Russia to expand the use of its nuclear weapons in retaliation in the event of an external attack.

The new decree signed by Putin also allows for the use of nuclear weapons in retaliation against any significant conventional attack on Russia, including drone strikes.

“Aggression by a non-nuclear state with the participation of a nuclear state is considered a joint attack,” Peskov told reporters on Tuesday — a clear reference to Ukraine and its Western backers.

This move to review the policy comes a month after Putin’s earlier remarks about revising the doctrine in light of perceived threats from allied states.

Putin earlier issued stern warnings to the US and its European allies, warning that allowing Ukraine to strike deep into Russian territory with advanced Western weaponry could escalate tensions and lead to direct conflict with Russia.