Western military alliance Nato has formally accused Russia of breaching the 1987 Intermediate-range Nuclear Forces (INF) Treaty, which banned land-based nuclear missiles in Europe.
Following a meeting, Nato foreign ministers issued a statement supporting US accusations of Russian violations.
The US has threatened to withdraw from the treaty because of Russian actions.
Russia denied being in breach of the INF deal, saying it “strictly abides” by its conditions.
The deal banned ground-launched medium-range missiles with a range of 500-5,500km (310-3,400 miles).
“Allies have concluded that Russia has developed and fielded a missile system, the 9M729, which violates the INF Treaty and poses significant risks to Euro-Atlantic security,” the Nato foreign ministers’ statement reads.
“We strongly support the finding of the United States that Russia is in material breach of its obligations under the INF Treaty.
“We call on Russia to return urgently to full and verifiable compliance. It is now up to Russia to preserve the INF Treaty.”
The new medium-range missile that the US – and now Nato – accuse Russian of deploying would enable Russia to launch a nuclear strike at Nato countries at very short notice.
Analysts say Russia sees such weapons as a cheaper alternative to conventional forces.
Speaking after the Nato statement was issued, US Secretary of State Mike Pompeo said Russia had 60 days to return to compliance with the treaty, after which time the US would suspend its own compliance.
“During this 60 days we will still not test or produce or deploy any systems, and we’ll see what happens during this 60-day period,” he said.