Russia must halt its covert development of a banned cruise missile system or the United States will seek to destroy it before it becomes operational, Washington's envoy to NATO has warned.

Key points: The US believes Russia is developing weapons in violation of a treaty

The US believes Russia is developing weapons in violation of a treaty Washington's NATO envoy says the US is prepared to consider a military strike

Washington's NATO envoy says the US is prepared to consider a military strike Russia says "aggressive rhetoric" from the US is dangerous

The United States believes Russia has breached a Cold War treaty by developing a ground-launched system that could allow Russia to launch a nuclear strike on Europe at short notice, but Moscow has consistently denied any such violation.

US ambassador to NATO Kay Bailey Hutchison said Washington remained committed to a diplomatic solution but was prepared to consider a military strike if Russian development of the medium-range system continued.

"At that point, we would be looking at the capability to take out a [Russian] missile that could hit any of our countries," she told a news conference.

"Counter measures [by the United States] would be to take out the missiles that are in development by Russia in violation of the treaty.

"They are on notice."

Ms Hutchinson then took to Twitter to assert that her comments did not mean the US would pre-emptively strike Russia.

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She said that Russia needed to comply with the treaty, or "we will need to match its capabilities to protect US and NATO interests".

She added that the current situation is "untenable".

Russian President Vladimir Putin earlier this year said his country possessed new advanced nuclear weapons that made NATO's missile defence "useless".

He said these included a nuclear-powered cruise missile, a nuclear-powered underwater drone and new hypersonic missiles.

At that time, the Trump administration said it was fully prepared for those weapons and accused Russia of violating its treaty obligations.

The 1987 Intermediate-Range Nuclear Forces Treaty bans medium-range missiles capable of hitting Europe or Alaska.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 27 seconds 27 s Mr Putin said his country's missiles could not be intercepted.

'Aggressive rhetoric' dangerous: Russia

The comments by Ms Hutchison are the most direct warning since a US official said in 2017 that the United States would consider its own missile system if Russia continued to violate the treaty.

But that same year, a US State Department report found Russia had violated obligations "not to possess, produce, or flight-test" such missiles, "or to possess or produce launchers" for them.

Russia's foreign ministry said it regarded Ms Hutchison's statement as dangerous. In the past, it has said it was ready for talks with the United States to try to preserve the treaty and would comply with its obligations if the United States did.

"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 foreign ministry spokeswoman Maria Zakharova as saying.

The US 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 Russian 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," Ms Hutchison said.

"We are laying down the markers so that our allies will help us bring Russia to the table," she added.

US Secretary of Defence 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," he told reporters in Paris.

"I'll return with the advice of our allies and engage in that discussion to determine the way ahead."

ABC/Reuters