The Kremlin on Monday said Western criticism would not change plans announced by President Vladimir Putin to deploy tactical nuclear weapons in neighbouring Belarus.
The West condemned Putin's weekend announcement on placing the weapons in EU and NATO-bordering Belarus, triggering calls for new sanctions on Moscow.
Ukraine said it was seeking an emergency meeting of the UN Security Council over the move.
"Such a reaction of course cannot influence Russian plans," Kremlin spokesman Dmitry Peskov said.
Speaking during a televised interview on Saturday, Putin said Moscow would station the tactical nuclear weapons "without violating our international agreements on nuclear non-proliferation".
He said this was "nothing unusual".
"The United States has been doing this for decades. They have long placed their tactical nuclear weapons on the territory of their allies," Putin said.
The Russian leader said he spoke to his Belarusian ally Alexander Lukashenko and that they had "agreed to do the same".
Putin's announcement came over a year into his grinding offensive in Ukraine.
In Washington, State Department spokesman Vedant Patel reiterated that the United States was not changing its own nuclear posture and did not have reason to believe Russia was preparing to use a nuclear weapon.
"But candidly, this announcement is one that we condemn. This is the latest example of irresponsible nuclear rhetoric that we have seen from Russia," Patel told reporters.
"No other country has raised the prospect of potential nuclear use in connection with this conflict. Let's remember -- no country is threatening Russia or threatening President Putin," Patel said.
