NATO expressed on Friday "serious concerns" over a Russian missile system which it says threatens to violate a Cold War arms treaty.
"NATO urges Russia to address these concerns in a substantial and transparent way, and actively engage in a technical dialogue with the United States," a statement read.
The U.S. accuses Moscow of violating the Intermediate-Range Nuclear Forces treaty, which bans the production, possession or testing of a ground-fired cruise missile.
This treaty, which was reached between the United States and the Soviet Union in 1987, has been "crucial" to Euro-Atlantic security, according to the statement.
"The Alliance is united in its appreciation that effective arms control agreements remain an essential element to strategic stability and our collective security," it added.
