Russia will deploy tactical nuclear weapons to its ally Belarus, President Vladimir Putin said Saturday, delivering a warning to the United States and European nations supporting Ukraine in its fight against Moscow's aggression.

The move could mark the first time Russia deployed nuclear weapons outside its country following the withdrawal of such arms from former Soviet Union republics in the wake of its 1991 collapse.

Russian President Vladimir Putin. (Anadolu Agency/Getty/Kyodo)

The possible deployment of tactical nuclear weapons -- designed for use on the battlefield for limited strikes -- could heighten tensions between Russia and the North Atlantic Treaty Organization. The U.S. government has shown a measured response, saying it has not seen any signs Russia is preparing to use a nuclear weapon.

In an interview with a state-run television network, Putin said a storage facility for tactical nuclear weapons will be completed on July 1 on the Belarusian territory.

"The United States has been doing this for decades," the Russian leader was quoted as saying by Russia's Tass news agency. "They placed their tactical nuclear weapons on the territories of their allied countries, NATO countries, in Europe a long time ago."

He said Russia agreed with Belarus to "do the same" while insisting that Moscow has no intention of violating its international obligations on the nonproliferation of nuclear weapons.

Russia began its offensive against its neighbor over a year ago after asserting that its own security is under threat from the potential expansion of NATO and the possibility of Ukraine joining the alliance.

Russia has helped Belarus upgrade its 10 military aircraft to be capable of carrying nuclear weapons and also handed over the Iskandar nuclear-capable ballistic missile system.

Belarus, which shares borders with NATO countries, including Poland, has aided Russia in its military aggression, although it has not taken part in the invasion directly.

The United States will continue to "monitor the implications" of the latest announcement while committing to the collective defense of the NATO alliance, Vedant Patel, principal deputy spokesman of the State Department, said in a statement.

He also said, "We have not seen any reason to adjust our own strategic nuclear posture nor any indications Russia is preparing to use a nuclear weapon."