Former Russian President Dmitry Medvedev has warned NATO that the defeat of his country as a nuclear power in Ukraine could trigger a nuclear war.
"The defeat of a nuclear power in a conventional war may trigger a nuclear war," Medvedev said in a post on Telegram on Thursday.
Medvedev, who now serves as deputy chairman of President Vladimir Putin's security council, said, "Nuclear powers have never lost major conflicts on which their fate depends."
Russia and the United States, the largest nuclear powers, hold around 90% of the world's nuclear warheads.
Medvedev made the warning ahead of a planned meeting of dozens of NATO and other defense leaders from roughly 50 countries at Ramstein Air Base in Germany on Friday.
He said those who are due to meet at the airbase to talk about strategy and support for the West's attempts to defeat Russia in Ukraine should think about the risks of their policy.
The focus of the meeting is expected to be on whether Germany will send its Leopard battle tanks to Ukraine or at least approve their transfer from third countries.
Pressure on German Chancellor Olaf Scholz intensified after Britain announced last weekend that it would send its own Challenger 2 battle tanks to Ukraine.
Germany has so far been cautious about approving weapons that could be seen by Russia as an escalation.
Russia has warned the West against sending military hardware to Ukraine, saying the move would prolong the war, which began in February last year.