Belarus said on Tuesday it was forced to host Russian nuclear weapons due to "unprecedented" Western pressure, insisting their deployment did not violate international agreements.
At the weekend Russian President Vladimir Putin announced plans to station tactical nuclear weapons in the Moscow-allied country, drawing condemnation from the West.
"Belarus is forced to respond to strengthen its own security and defence capability," the foreign ministry in Minsk said.
It said Minsk had been subjected to "unprecedented" political and economic pressure from the United States and its allies.
Belarus said it would not have control over the weapons and their deployment "in no way contradicts" the Treaty on the Non-Proliferation of Nuclear Weapons.
Minsk allowed Russia to use its territory as a launchpad for Moscow's offensive against Ukraine last year.
The two countries have since held military exercises on Belarusian territory and increased cooperation between their armies.
"Military cooperation between Belarus and Russia is carried out in strict accordance with international law," the foreign ministry said.
Putin's plans to place nuclear weapons on the European Union's doorstep have triggered calls for new sanctions against Moscow.
With fears of a nuclear war rising since Putin sent troops into Ukraine, experts believe that any Russian strike would probably involve "tactical" small-sized battlefield weapons as opposed to "strategic" high-powered long-range nuclear weapons.
Authoritarian President Alexander Lukashenko has ruled Belarus since 1994. The West has hit Minsk with multiple rounds of sanctions over its crackdown on political dissent and its role as a springboard for Moscow's assault on Ukraine.