Ukraine is requesting an emergency meeting of the United Nations Security Council on Sunday after Russia said it had reached an agreement to station nuclear weapons in Belarus, calling on the U.S. and other world powers to counter the Kremlin’s “nuclear blackmail.”

“Ukraine expects effective measures to counter the Kremlin’s nuclear blackmail by the United Kingdom, China, the USA and France, in particular, as permanent members of the UN Security Council,” Ukraine’s Foreign Ministry said in a statement. “We demand to immediately convene an extraordinary meeting of the UN Security Council for this purpose.”

The call for an emergency meeting at the U.N. by Ukraine comes after Russian President Vladimir Putin said on Saturday that his country would station tactical nuclear weapons in Belarus, which shares a border with both Russia and Ukraine. Tactical nuclear weapons are made for battlefield use and are not designed for wide-ranging effects like long-range nuclear weapons.

Putin framed the decision as a counter to the U.S. deployment of nuclear weapons in Europe, saying “we are doing what they have been doing for decades.”

But the move by Putin raised eyebrows as the West fears an intensified assault on Ukraine. While Belarus has not directly been involved in the fighting with its military — instead lending its land border with Ukraine for use to Russia — there have been fears that the country may get involved in the future.

Ukraine appealed to Belarus to not become a “hostage” of the Kremlin.

“Ukraine appeals to Belarusian society to prevent the fulfillment of the criminal purposes  regarding the deployment of nuclear weapons on the territory of Belarus … which will further turn this country into a hostage of the Kremlin,” the foreign ministry said in the statement.

National Security Council spokesman John Kirby said on CBS’s “Face The Nation” on Sunday that there had been “no indication” that Putin had made good on the pledge to move nuclear weapons to Belarus or that he planned to use them in the war in Ukraine.

“We have not seen any indication that he’s made good on this pledge or moved any nuclear weapons around,” Kelly said. “We’ve in fact seen no indication that he has any intention to use nuclear weapons, period, inside Ukraine.”