Russia moved ahead on Thursday with a plan to deploy tactical nuclear weapons in Belarus, whose leader said the warheads were already on the move, in the Kremlin's first deployment of such bombs outside Russia since the 1991 fall of the Soviet Union.
President Vladimir Putin says the United States and its allies are fighting an escalating proxy war against Russia after the Kremlin chief sent troops into Ukraine in February last year.
The plan for the nuclear deployment was announced by Vladimir Putin in an interview with state television on March 25.
"The collective West is essentially waging an undeclared war against our countries," President Putin's defence minister, Sergei Shoigu, said at a meeting with his Belarusian counterpart in Minsk, according to Russia's defence ministry.
The West, Mr Shoigu said, was doing all it could "to prolong and escalate the armed conflict in Ukraine."
Belarus President Alexander Lukashenko said that tactical nuclear weapons were already on the move after he said Vladimir Putin had signed an order, though there was no confirmation of that from the Kremlin itself.
"The movement of the nuclear weapons has already begun," President Lukashenko told reporters. Asked if the weapons were already in Belarus, he said: "Possibly. When I get back I will check."
Mr Shoigu said the documents he was signing in Minsk concerned the process for storing tactical nuclear weapons in a special facility in Belarus.
President Putin has repeatedly warned that Russia, which has more nuclear weapons than any other country, will use all means to defend itself, and he has cast the Ukraine war as a battle for the survival of Russia against an aggressive West.
The United States and its allies say they want Ukraine to defeat Russian forces on the battlefield but deny that they want to destroy Russia - and deny that the Ukraine war is in any way linked to post-Soviet enlargement of NATO.
It is still unclear exactly when the Russian tactical nuclear weapons will be deployed in Belarus, which has borders with three NATO members - Poland, Lithuania and Latvia. Russia will remain in control of the weapons.
Tactical nuclear weapons are nuclear weapons used for specific tactical gains on the battlefield, and so are usually smaller in yield than the strategic nuclear weapons designed to destroy the biggest cities of the United States or Russia.
Russia has a huge numerical superiority over the United States and the NATO military alliance when it comes to tactical nuclear weapons: the United States believes Russia has around 2,000 such working tactical warheads.
The United States has around 200 such tactical nuclear weapons, half of which are at bases in Europe. These 12-ft B61 nuclear bombs, with different yields of 0.3 to 170 kilotons, are deployed at six air bases across Italy, Germany, Turkey, Belgium and the Netherlands.
Mr Shoigu said that Iskander-M missiles, which can carry conventional or nuclear warheads, had been handed to the Belarusian armed forces, and some Su-25 aircraft had been converted for the possible use of nuclear weapons.
"Belarusian servicemen have received the necessary training," Sergei Shoigu was quoted as saying by his ministry. He said the two countries could take further measures to ensure their security.
"NATO's military activities have become as aggressive as possible," Mr Shoigu said.
The United States has said the world faces the gravest nuclear danger since the 1962 Cuban Missile Crisis because of remarks by Vladimir Putin during the Ukraine conflict, but Moscow says its position has been misinterpreted.
The Treaty on the Non-Proliferation of Nuclear Weapons, signed by the Soviet Union, says that no nuclear power can transfer nuclear weapons or technology to a non-nuclear power, but it does allow for the weapons to be deployed outside its borders but under its control.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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