Ukraine on Sunday fiercely criticized plans by Russian President Vladimir Putin to station tactical nuclear weapons in Belarus and called for an emergency U.N. Security Council session to address the move.
Putin announced the decision on Saturday, saying it would not violate nuclear non-proliferation promises and Russia would not hand off control of the weapons to Belarus.
In a statement, Kyiv's foreign ministry described it as "another provocative step" by Moscow that undermines "the international security system as a whole".
"Russia once again confirms its chronic inability to be a responsible steward of nuclear weapons as a means of deterrence and prevention of war, not as a tool of threats and intimidation," the ministry said.
It demanded a Security Council session and also called on the Group of Seven countries and the European Union to warn Belarus of "far-reaching consequences" if it decides to accept the Russian weapons.
Putin said in his remarks on Saturday that Belarus President Alexander Lukashenko had requested the stationing of the weapons. Minsk has not yet commented publicly on Putin's announcement.
The Belarusian army has not formally fought in Ukraine but Minsk allowed Moscow to use Belarusian territory to send troops into Ukraine last year. The two countries share a close military relationship.
"Ukraine calls on all members of the international community to convey to the criminal (P)utin regime the categorical unacceptability of its next nuclear provocations and to take decisive measures to effectively deter and prevent any possibility of the aggressor state's use of nuclear weapons," the Ukrainian statement said.