Russia urged the United States on Friday to clarify what it called contradictory signals about a resumption of nuclear testing, saying such a step would trigger responses from Russia and other countries.
President Donald Trump last week ordered the US military to immediately restart the process for testing nuclear weapons. But he did not make clear if he meant flight-testing of nuclear-capable missiles or a resumption of tests involving nuclear explosions - something neither the US nor Russia has done for more than three decades.
"If it is the latter, then this will create negative dynamics and trigger steps from other states, including Russia, in response," Russian Foreign Ministry spokeswoman Maria Zakharova told reporters.
"For now, we note that the signals emanating from Washington, which are causing justified concern in all corners of the world, remain contradictory, and, of course, the real state of affairs must be clarified."
Citing the lack of clarity around US plans, President Vladimir Putin on Wednesday instructed top officials to prepare proposals for Russia to carry out its own potential nuclear test in response to any US test.
Security analysts say a resumption of testing by any of the world's nuclear powers would be a destabilizing step at a time of acute geopolitical tension, notably over the war in Ukraine, and would likely prompt other countries to follow suit.
Russia and the US possess the world's largest nuclear arsenals.
The last remaining treaty between them that limits the number of strategic nuclear warheads on both sides is due to expire in three months, potentially fueling an arms race that is already in progress.
Putin has proposed that both sides continue to observe the treaty limits for another year, but Trump has yet to respond formally to the idea.
