By Guy Faulconbridge

LONDON: One of President Vladimir Putin's closest allies warned the United States on Wednesday that the world could spiral towards a nuclear dystopia if Washington pressed on with what the Kremlin casts as a long-term plot to destroy Russia.

Dmitry Medvedev, who was president from 2008 to 2012 and is now deputy secretary of Russia's Security Council, said the United States had conspired to destroy Russia as part of an "primitive game" since the 1991 fall of the Soviet Union.

"It means Russia must be humiliated, limited, shattered, divided and destroyed," Medvedev, 56, said in a 550-word statement.

The views of Medvedev, once considered to be one of the least hawkish members of Putin's circle, gives an insight into the thinking within the Kremlin as Moscow faces in the biggest confrontation with the West since the 1962 Cuban Missile Crisis.

The United States has repeatedly said that it does not want the collapse of Russia and that its own interests are best served by a prosperous, stable and open Russia.

The State Department did not immediately respond to a request for comment outside usual business hours.

Russia's invasion of Ukraine has killed thousands of people, displaced nearly 10 million and raised fears of a wider confrontation between Russia and the United States - the world's two biggest nuclear powers.

Putin says the operation was necessary because the United States was using Ukraine to threaten Russia and Moscow had to defend against the "genocide" of Russian speakers by Ukraine. Ukraine says Putin's claims of genocide are nonsense.

Medvedev said the Kremlin would never allow the destruction of Russia, but warned Washington that if it did achieve what he characterised as its destructive aims then the world could face a dystopian crisis that would end in a "big nuclear explosion".

He also painted a picture of a post-Putin world that would follow the collapse of Russia, which has more nuclear warheads than any other country.

The destruction of the world's biggest country by area, Medvedev said, could lead to an unstable leadership in Moscow "with a maximum number of nuclear weapons aimed at targets in the United States and Europe."

Russia's collapse, he said, would lead to five or six nuclear armed states across the Eurasian landmass run by "freaks, fanatics and radicals".

"Is this a dystopia or some mad futuristic forecast? Is it Pulp fiction? No," Medvedev said.