Russia regards as dangerous a statement by Washington's envoy to NATO who said Moscow must halt its covert development of a banned cruise missile system or the United States would seek to destroy it before it becomes operational.
The U.S. ambassador to NATO, Kay Bailey Hutchison, said early Tuesday Washington remained committed to a diplomatic solution but was prepared to consider a military strike if Russian development of the medium-range system continued.
"It seems that people who make such statements do not realise the level of their responsibility and the danger of aggressive rhetoric," TASS news agency quoted Russia's Foreign Ministry spokeswoman Maria Zakharova as saying.
Hutchison later clarified in a tweet that she was not talking about a preemptive strike against Russia. "My point: Russia needs to return to INF Treaty compliance or we will need to match its capabilities to protect US & NATO interests. The current situation, with Russia in blatant violation, is untenable."
The 1987 Intermediate-Range Nuclear Forces Treaty bans medium-range missiles capable of hitting Europe or Alaska.
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In Washington, State Department spokeswoman Heather Nauert said the United States had for some time argued that Moscow was not in compliance with the treaty.
"What Ambassador Hutchison was talking about was improving overall defense and deterrence posture," Nauert told a news conference. "The United States is committed to upholding its arms control obligations and expects Russia to do the very same thing," she said, adding that the U.S. was discussing the issue with its allies.
A U.S. State Department report found Russia had violated obligations "not to possess, produce, or flight-test" a ground-launched cruise missile with a range capability of 500 km to 5,500 km (310-3,420 miles), "or to possess or produce launchers of such missiles."
The U.S. accusations are likely to further strain relations between Moscow and the West that are at a low over Russia's 2014 seizure of Crimea, its bombing campaign in Syria and accusations of meddling in Western elections.
"We have been trying to send a message to Russia for several years that we know they are violating the treaty; we have shown Russia the evidence that we have that they are violating the treaty," Hutchison said.
"We are laying down the markers so that our allies will help us bring Russia to the table," she added.
U.S. Secretary of Defense Jim Mattis said he would discuss the issue with his NATO counterparts at a scheduled two-day meeting in Brussels from Wednesday.
"I cannot forecast where it will go, it is a decision for the president, but I can tell you that both on Capitol Hill and in State Department, there is a lot of concern about this situation and I'll return with the advice of our allies and engage in that discussion to determine the way ahead," he told reporters in Paris.