Medvedev, once seen in the West as a liberal moderniser, has emerged as one of Russia's most outspoken hawks since Moscow launched what it called a "special military operation" in Ukraine last year.
A nuclear war was "quite probable" but was unlikely to have any winners, said Medvedev, who has repeatedly said Western support for Ukraine increases the chances of nuclear conflict.
Medvedev said Moscow was still committed to stopping Ukraine join NATO.
Given NATO's rule about not admitting countries entangled in territorial conflicts, he said the conflict with Ukraine could become "permanent" given its existential nature for Moscow.
The only way to de-escalate tensions between Russia and the West was to enter into tough negotiations, he said.
Persons:
Dmitry Medvedev, Russia's, Medvedev, Andrew Osborn, Guy Faulconbridge, Frank Jack Daniel Our
Organizations:
NATO, LONDON, West, Security Council, Gazeta, Thomson
Locations:
Russia, Cuban, Moscow, Ukraine, Kyiv, United States