Vladimir Putin has announced plans to station tactical nuclear weapons in Belarus.
Putin claimed the move would not violate non-proliferation agreements and compared it to the US stationing weapons in Europe.
Moscow would maintain control of the weapons, he said.
Russia has used the territory of Belarus, a firm Kremlin ally, as a staging post to send troops into Ukraine, and the two countries maintain close military ties.
It would be the first time since the mid-1990s that Russia has stationed nuclear weapons outside Russia.
Storage facilities are due to be completed by July 1, although Putin did not specify when the weapons would be transferred.
Putin told Russian state television on Saturday that Belarusian leader Alexander Lukashenko had long raised the issue of stationing tactical nuclear weapons in Belarus.
“There is nothing unusual here either," he said. “Firstly, the United States has been doing this for decades.
“They have long deployed their tactical nuclear weapons on the territory of their allied countries.”
Tactical nuclear weapons are intended for use on the battlefield, unlike more powerful, longer-range strategic nuclear weapons.
Russia has stationed 10 aircraft in Belarus capable of carrying tactical nuclear weapons, Putin said, adding that Moscow had already transferred to Belarus a number of Iskander tactical missile systems that can launch nuclear weapons.
Analysts said the move was intended to intimidate Nato, the military alliance of Western countries.
"This is part of Putin’s game to try to intimidate Nato ... because there is no military utility from doing this in Belarus as Russia has so many of these weapons and forces inside Russia,” analyst Hans Kristensen told Reuters.
Belarus borders Nato members - Poland, Lithuania and Latvia.
It comes after Ukraine’s president Volodymyr Zelensky said his country could not yet launch a counter-offensive against Russia’s invasion without more artillery from the West.
He said in a newspaper interview: “We can’t start yet, we can’t send our brave soldiers to the front line without tanks, artillery and long-range rockets.”