As reported by Censor.NET citing The Guardian, U.S. NATO Envoy Kay Bailey Hutchison was speaking to reporters about a longstanding issue of contention, a Russian ground-launched cruise missile which Washington says breaks the 1987 Intermediate-Range Nuclear Forces Treaty (INF).
Moscow has denied the charge, and the Trump administration has announced plans to develop its own medium-range cruise missile in response, raising the spectre of a new nuclear arms race.
But Hutchison went further in her remarks and appeared to suggest the possibility of a pre-emptive strike when the Russian missiles became operational.
"The counter-measures would be to take out the missiles that are in development by Russia in violation of the treaty," the envoy said, mistakenly referring to the missile in question as a ballistic missile, rather than a cruise missile. She also suggested the missile, known as 9M729, was still in development, but the U.S. accused Russia of deploying it last year.
"Getting them to withdraw would be our choice, of course. But I think the question was what would you do if this continues to a point where we know that they are capable of delivering. And at that point we would then be looking at a capability to take out a missile that could hit any of our countries in Europe and hit America in Alaska."
The Russian foreign ministry accused Hutchison of dangerous rhetoric.
"It seems that people who make such statements do not realise the level of their responsibility and the danger of aggressive rhetoric," the ministry spokeswoman, Maria Zakharova, said, according to Tass news agency.
A few hours later, Hutchison clarified her remarks on Twitter, insisting she was "not talking about preemptively striking Russia", adding that Russia "needs to return to INF Treaty compliance or we will need to match its capabilities to protect U.S. and NATO interests".
Hutchison did not specifically explain what she meant by her warning that the U.S. would "take out" the Russian missile.
A U.S. threat of a pre-emptive strike against Russia would be unprecedented since the end of the cold war, and a dangerous new departure in rhetoric and military posture towards Russia.
"If she is saying that if the diplomatic route doesn’t work we will destroy the missiles, that’s obviously dangerous and risks triggering a war that could go nuclear," Daryl Kimball, the head of the Arms Control Association, said. "I cannot recall anything like this in the post cold-war period."
Some nuclear experts speculated that Hutchison may have misspoken, and meant to say that the US would develop ways of destroying the Russian missile for use in the event of a conflict.
Hans Kristensen, the director of the nuclear information project at the Federation of American Scientists, said: "I don’t think the Nato ambassador is threatening pre-emptive attacks against Russian development of INF weapons. She did a poor job in trying to repeat what the US has been saying for several years; that it is contemplating measures in response to the Russian INF violation.
"That can include tweaking existing strike capabilities to hold the new weapons at risk, developing new ones for potential deployment, and/or increasing economic and political pressure on Moscow to return to compliance."
Kristensen said: "This is going to feed right into the paranoia of Russian planners. She will definitely have to make a follow-up statement to clarify what she intended to say."