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.
US President Donald Trump later said there was a "very good chance we'll reach a new agreement" with Russia.
"I think we have a very good relationship with Russia, but Russia didn't adhere to the treaty," Mr Trump said on Thursday, adding: "Until they adhere we will pull out."
The US will formally withdraw from the accord 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.
Some 35 nations are party to the treaty, including Russia, Canada and the UK.
How has Russia responded?
Russia's Foreign Ministry insisted that it had not violated the treaty and that a US withdrawal would be "very regrettable", adding that the Trump administration was working to "derail all agreements on arms control".
"We reject any attempts to justify a way out of this fundamental agreement," Russian Deputy Foreign Minister Alexander Grushko told Russia's state-owned RIA Novosti news agency.
"Nothing prevents continuing the discussions over the technical issues, which the US is misrepresenting as violations by Russia," he added.
He said that any withdrawal would affect the interests of all of the treaty's participants, who are also members of the North Atlantic Treaty Organisation (Nato).
A development to trouble US allies
In abandoning the Open Skies Treaty, the Trump Administration is not just renouncing an arms control agreement that was seen as essential for transparency during the 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 great power competition beckons is doubly troubling.
The Open Skies Treaty came into force in January 2002 and some 34 countries have ratified the agreement. It allows for unarmed short-notice reconnaissance flights by specially equipped aircraft, over the entire territory of another country to collect data on troop deployments, military facilities and so on.
There have been some problems in recent years and the US contends – with some justification – that Russia has been preventing access to certain areas. But critics of the Trump administration's antipathy towards arms control say this is a reason for fixing the treaty, not abandoning it.
Mr Trump seems to be holding out at least a chance that the US could stick with Open Skies, but that is clearly going to depend upon talks with Moscow.
The Russian Foreign ministry says that a US withdrawal will affect the interests of all the participants. While the US can clearly use satellites for its intelligence gathering on Russia, Mr Trump's decision will cause tensionRead More – Source