Dmitry Medvedev, a long-time ally of Russian President Vladimir Putin, has laid out the country's new deterrence policy against Western "aggression," and warned that provocations by Ukraine and its allies could result in nuclear war.

Putin, who casts the West as a decadent aggressor, and U.S. President Joe Biden, who casts Russia as a corrupt autocracy and Putin as a killer, have both warned that a direct Russia-NATO confrontation could escalate into World War Three.

MOSCOW, Sept 25 (Reuters) - President Vladimir Putin said on Wednesday that Russia could use nuclear weapons if it was attacked by any state and that any conventional attack on Russia that was supported by a nuclear power would be considered to be a joint attack.