The US has announced it will withdraw from a major accord that permits unarmed aerial surveillance flights over dozens of participating countries.
The Open Skies Treaty came into force in 2002 and is designed to boost confidence and assure against attacks.
But senior US officials said the country was withdrawing due to repeated Russian violations of its terms.
The US will inform Russia of its decision on Friday and formally withdraw in six months, officials said.
“During the course of this review it has become abundantly clear that it is no longer in America’s interests to remain a party to the Open Skies Treaty,” one official told Reuters news agency.
Russia’s Foreign Ministry said a US withdrawal would be “very regrettable”, adding that the Trump administration was working to “derail all agreements on arms control”.
Some 35 nations are party to the treaty, including Russia, Canada and the UK.
A development to trouble US allies
In abandoning the Open Skies Treaty, President Donald Trump is renouncing an arms control agreement that was seen as essential for transparency during the immediate post-Cold War years. But he is also ditching an agreement that many experts believe still retains huge benefits for the US.
The fact it comes at a time when the whole structure of arms control is collapsing and a new era of competition beckons is doubly troubling.
So what does the treaty permit?
It allows for unarmed short-notice reconnaissance flights by specially equipped aircraft over the entire territory of another country. These can be to collect data on troop deployments and military facilities, for example.
There have been some problems in recent years, and the US contends that Russia has been preventing access to some areas. But critics of the Trump Administration say this is a reason for fixing the treaty, not abandoning it.
The US can use satellites for its intelligence-gathering on Russia, but Mr Trump’s decision will cause tensions with European allies who do not have access to such technology. And it may be in Russia’s interest to remain in the treaty, exacerbating the unease of Washington’s partners, while it continues its flights over their territory.
Earlier this year, US Defence Secretary Mark Esper accused Russia of violating the treaty by banning flights over the city of Kaliningrad and other areas near Georgia.
“I have a lot of concerns about the treaty as it stands now,” he said at the time. “This is important to many of our NATO allies, that they have the means to conduct the overflights.”
It marks the latest effort by President Donald Trump’s administration to withdraw the US from a major global treaty.
Last year, it pulled out of the Intermediate-Range Nuclear Forces Treaty (INF) with Russia.
The INF was signed by the US and the USSR in 1987, and banned the vast majority of nuclear and non-nuclear missiles with short and medium ranges.