Video report by ITV News Washington Correspondent Robert Moore
The Trump administration said it is freeing itself from the constraints of a nuclear arms control treaty with Russia and will begin withdrawing from the pact on Saturday.
The move has caused concern among analysts who worry it could spark a new arms race.
President Donald Trump said in a statement that Russia, "for far too long," has violated the Intermediate-Range Nuclear Forces treaty "with impunity, covertly developing and fielding a prohibited missile system that poses a direct threat to our allies and troops abroad."
He said the US "has fully adhered" to the pact for more than 30 years, "but we will not remain constrained by its terms while Russia misrepresents its actions. We cannot be the only country in the world unilaterally bound by this treaty, or any other."
Minutes after the US announcement, NATO said that if Moscow failed to destroy all new missile systems that Washington insists violate the treaty, "Russia will bear sole responsibility for the end of the treaty."
The withdrawal had been expected for months, and follows years of unresolved dispute over Russian compliance with the 1987 pact, which bans certain ground-launched cruise missiles.
Russia denies violating the treaty, but US secretary of state Mike Pompeo said Washington will suspend its obligations to the pact on Saturday and if Moscow does not come into compliance, it “will terminate”.
What is the treaty and why are the US worried about it?
The Intermediate-Range Nuclear Forces, or INF, treaty was the first arms control measure to ban an entire class of weapons: ground-launched cruise missiles with a range between 500 kilometers (310 miles) and 5,000 kilometers (3,100 miles).
US officials also have expressed worry that China, which is not party to the 1987 treaty, is gaining a significant military advantage in Asia by deploying large numbers of missiles with ranges beyond the treaty's limit. Leaving the INF treaty would allow the Trump administration to counter the Chinese, but it's unclear how it would do that.
Secretary of State Mike Pompeo said in early December that Washington would give Moscow 60 days to return to compliance before it gave formal notice of withdrawal, with actual withdrawal taking place six months later.
The 60-day deadline expires on Saturday, and the administration is expected to say as early as Friday that efforts to work out a compliance deal have failed.
Technically, a US withdrawal would take effect six months after this week's notification, leaving a small window for saving the treaty. However, in talks this week in Beijing, the U.S. and Russia reported no breakthrough in their dispute, leaving little reason to think either side would change its stance on whether a Russian cruise missile violates the pact.
What is Russia's response?
A Russian deputy foreign minister, Sergei Ryabkov, was quoted by the Russian state news agency Tass as saying after the Beijing talks Thursday, "Unfortunately, there is no progress. The position of the American side is very tough and like an ultimatum."
He said he expects Washington now to suspend its obligations under the treaty, although he added that Moscow remains ready to "search for solutions" that could keep the treaty in force.
US withdrawal raises the prospect of further deterioration in U.S.-Russian relations, which already are arguably at the lowest point in decades.
The US has no nuclear-capable missiles based in Europe; the last of that type and range were withdrawn in line with the INF treaty.
Nuclear weapons experts at the Carnegie Endowment for International Peace said in a statement this week that while Russia's violation of the INF treaty is a serious problem, US withdrawal under current circumstances would be counterproductive.
"Leaving the INF treaty will unleash a new missile competition between the United States and Russia," they said.