Jim Michaels

USA TODAY

WASHINGTON — The United States on Monday accused Russia of violating a 1987 nuclear missile treaty that prohibits having or testing intermediate range cruise missile.

A State Department official called the alleged violation a "very serious matter which we have attempted to address with Russia for some time now." The official asked not to be named in order to discuss sensitive issues.

The American accusation comes at a tense time for U.S.-Russian relations. The United States has accused Russia of supporting separatists in Ukraine even after the rebels were suspected of shooting down a commercial airliner over rebel territory.

The Russians are accused of violating terms of the Intermediate-Range Nuclear Forces Treaty which prohibits possessing or testing cruise missiles with a range of between 500 and 5,500 kilometers.

The United States has notified Russia of the alleged violation, the official said.

The United States plans to discuss the issue "with the aim of assuring the United States that Russia will come back into compliance with its treaty obligations," the official said.

The U.S. says Russia tested a new ground-launched cruise missile, breaking the Intermediate-Range Nuclear Forces Treaty that President Ronald Reagan signed with Soviet leader Mikhail Gorbachev.

Contributing: The Associated Press