Russian Foreign Minister Sergei Lavrov has accused Ukraine of threatening international security.
The government in Kiev wants its own nuclear weapons, Lavrov told the permanent Conference on Disarmament in Geneva via video link on Tuesday.
Soviet nuclear technology and the means to shoot down weapons armed in this way are still on Ukrainian territory, Lavrov said, according to the UN's English translation.
"We cannot fail to respond to this real danger," Lavrov said, while also demanding that US nuclear weapons be withdrawn from the territory of NATO partners.
"We continue to believe that a nuclear war cannot be won and must never be fought," Lavrov said.
The Conference on Disarmament is the only multilateral disarmament forum in the world.
The International Atomic Energy Agency (IAEA) said last week it saw no evidence to support claims of a possible nuclear weapons programme in Ukraine.
"Our agency has found no evidence that declared nuclear material is being diverted from the peaceful use of nuclear energy in Ukraine," an IAEA spokesman told the German-language Tagesspiegel newspaper.
Prevent new arms race
The Vienna-based agency monitors the civilian use of nuclear power and compliance with the Nuclear Non-Proliferation Treaty under the umbrella of the UN.
Lavrov went on to say that a new arms race must be prevented. There must be no dangerous steps in the context of military rearmament. NATO members were ignoring this and were dragging Ukraine into the alliance's orbit by supplying it with weapons, Lavrov said.
He complained that NATO was not giving Russia any long-term security guarantees and was not ruling out further expansion towards the east.
NATO must withdraw its military capabilities to the area where they were when the NATO-Russia Founding Act on Mutual Relations, Cooperation and Security was signed in 1997, Lavrov demanded.
Lavrov originally wanted to come to Geneva in person but was prevented from doing so by the closure of airspace in the EU to Russian aircraft, the Russian embassy in Geneva announced on Monday.