The United States has found that Russia violated a 1987 arms control treaty by testing a ground-launched cruise missile, a senior US official has said, calling the matter "very serious."
The announcement adds a new dispute at a time of already heightened tensions between Washington and the Kremlin over the crisis in Ukraine.
Western countries have accused Russia of arming Ukrainian separatists and destabilising the country.
The US concluded in a 2014 report that Russia had violated the Intermediate-Range Nuclear Forces Treaty, which barred it from possessing, producing or flight-testing such cruise missiles with a range of 500 to 5,500km, the official said.
President Barack Obama has sent a letter to Russia President Vladimir Putin on the subject.
The administration official described as it "a very serious matter, which we have attempted to address with Russia for some time now."
The Intermediate-Range Nuclear Forces Treaty, signed by then US president Ronald Reagan and his Russian counterpart Mikhail Gorbachev, eliminated nuclear and conventional intermediate range ground-launched ballistic and cruise missiles.
The official said the INF treaty served the "mutual security interests of the parties" - not only the US and Russia but also 11 other successor states of the Soviet Union.
"Moreover, this treaty contributes to the security of our allies and to regional security in Europe and in the Far East."
"The United States will, of course, consult with allies on this matter to take into account the impact of this Russian violation on our collective security if Russia does not return to compliance," the official said.
In January, State Department spokeswoman Jen Psaki said Washington had raised concerns with Moscow following a New York Times report it had begun testing a new ground-launched cruise missile as early as 2008, and that the State Department's senior arms control official had repeatedly raised the issue with Moscow since May 2013.
Ms Psaki said at the time she could not refute the details of the Times report, and that there was an ongoing inter-agency review to determine whether the Russians had violated the terms of a US-Russian arms control pact.