Vladimir Putin has said that a battery of tactical nuclear weapons have been stationed in Belarus.
The Russian president told a forum that the lethal munitions would only be used if Russia's territory or state was under threat.
The US government has said that there is no indication the Kremlin plans to attack Ukraine with the weapons, the BBC reports.
"We don't see any indications that Russia is preparing to use a nuclear weapon," US Secretary of State Antony Blinken said following Mr Putin's comments.
Mr Putin said that the full transfer of weapons to Belarus - a key ally and launchpad for his invasion of Ukraine - would be completed by the end of the summer.
He told the St Petersburg International Economic Forum that the move was about "containment" and to remind any of his adversaries who may be "thinking of inflicting a strategic defeat on us".
When asked if he would consider using the weapons, he replied: "Why should we threaten the whole world? I have already said that the use of extreme measures is possible in case there is a danger to Russian statehood."
Putin went on: “Nuclear weapons are created to ensure our security in the broadest sense of the word and the existence of the Russian state. But we, firstly, do not have such a need.
"Extreme means may be used if there is a threat to Russia’s statehood. In this case, we will certainly use all the forces and means that the Russian state has at its disposal.”
He added: "Just talking about this lowers the nuclear threshold. We have more than NATO countries and they want to reduce our numbers. Go to hell."
Tactical nuclear weapons are designed to be used on the battlefield or for a limited strike.
They are smaller nuclear warheads and delivery systems and are primed to destroy enemy targets with precision and without causing widespread radioactive fallout.
Nuclear weapons range from one kiloton - as is the case with tactical munitions - to as big as 100 kilotons.
For context, the atomic bomb dropped by the US military in Hiroshima in 1945 was 15 kilotons.
Mr Putin also took the opportunity to defend his sending of troops into Ukraine and repeated his claims that the Ukrainian government is a neo-Nazi regime, despite President Volodymyr Zelensky’s Jewish roots.
“My Jewish friends say that Zelensky is not a Jew, but a shame to the Jewish people,” Mr Putin said.
