BRUSSELS (AP) — The United States is urging Russia to prove it's honoring a landmark nuclear arms treaty from the Soviet era or to prepare for the pact to collapse.

Russia insists it is honoring the 1987 Intermediate Range Nuclear Forces (INF) Treaty. But NATO fears the 9M729 ground-fired cruise missile system Russia is developing would allow it to launch a nuclear strike in Europe with little or no notice.

The U.S. ambassador to NATO, Kay Bailey Hutchison, said on Tuesday that "if Russia doesn't come into compliance, they will face the consequence of not having a treaty."

Hutchison warned of "a time-frame" after which the U.S. "will not be able to allow Russia to have the capability that we agreed neither of us would have without getting a deterrent opportunity as well."