BRUSSELS — NATO repeated its support for the United States’ decision to abandon the 1987 Intermediate-Range Nuclear Forces agreement on Friday and said it would respond in a “measured and responsible way” to a deployment of missiles by Moscow that violated the pact.

“Russia bears sole responsibility for the demise of the treaty,” the alliance said in a statement, repeating accusations that Russia had long been out of compliance by deploying medium-range missiles with both conventional and nuclear capability. Russia denies breaching the pact.

“There are no new NATO missiles in Europe, but there are many, many, many new Russian missiles,” Jens Stoltenberg, the alliance’s secretary-general, said at a news conference. “We don’t want a new arms race, and we have no intention to deploy new land-based nuclear missiles in Europe.”

Washington has for six years accused Russia of developing a new type of missile, the 9M729, also known as the SSC-8, which it says violates the treaty. The missile has a range estimated to be about 900 miles, though Moscow says it can travel only about 300 miles.