The United States warned Russia and Belarus at a U.N. arms control meeting on Thursday not to deploy nuclear arms in Moscow's neighbouring ally following the Russian invasion of Ukraine.
"Any movement of Russian nuclear weapons into Belarus would be dangerously provocative and further destabilize the region. We call on Belarus to reject Russia's policies of nuclear threat and intimidation," U.S. envoy Aud-Frances McKernan told the Conference on Disarmament (CD) in remarks provided by the U.S. mission.
Her comments come as the Geneva-based CD debated Russia's invasion after Kyiv accused Moscow at the forum of "violating all key disarmament treaties".
A referendum in Belarus on Sunday approved a new constitution ditching the country's non-nuclear status at a time when the former Soviet republic has become a launch pad for Russia's military operation, Russian news agencies said.
The new constitution could see nuclear weapons on Belarusian soil for the first time since the country gave them up after the 1991 break-up of the Soviet Union.
Ukrainian Foreign Minister Dmytro Kuleba had said this week that Russian shelling during its offensive amounted to war crimes.
Russia calls its actions in Ukraine a "special military operation" that it says is not designed to occupy territory but to destroy its southern neighbour's military capabilities and capture what it regards as dangerous nationalists.
Russian Foreign Minister Sergei Lavrov told the CD meeting earlier this week that Kyiv had been seeking to acquire nuclear arms, saying Moscow needed to prevent that.
International Atomic Energy Agency chief Rafael Grossi told reporters in Vienna on Wednesday that the U.N. nuclear watchdog had no evidence to support Lavrov's allegation.
"For us it is very clear. We do not have any information that would question the non-proliferation credentials of Ukraine," Grossi said when asked about Lavrov's comment.
"It's important to say...that we continue our (nuclear) safeguards operation and we don't have information that there's any deviation of material, any undeclared material or activities leading to the development of nuclear weapons."
Some delegates saw the Ukraine crisis as an opportunity to revitalise the Conference on Disarmament, which has an ambitious formal mandate to negotiate weapons cuts but has not struck a deal since the 1996 Comprehensive Nuclear Test Ban Treaty.
However, experts said there was little hope of a concrete outcome on the allegations of Ukraine and other members against Russia since the 65-member forum must decide by consensus.
(Additional reporting by Stephanie Nebehay in Geneva and Francois Murphy in Vienna; Editing by Mark Heinrich)