The Pentagon on Thursday flight-tested a missile that had been banned under a treaty that the United States and Russia abandoned last summer. Some U.S. arms control advocates said the test risks an unnecessary arms race with Moscow.

The prototype missile was configured to be armed with a non-nuclear warhead. The Pentagon declined to disclose specifics beyond saying thew missile was launched from a “static launch stand” at Vandenberg Air Force Base in California and landed in the open ocean. The Defense Department said the ballistic missile flew more than 500 miles.
Russia said Friday it was alarmed after by the U.S.' test of a missile that would have been prohibited under the Intermediate-range Nuclear Forces Treaty.

Washington formally withdrew from the 1987 INF pact with Russia in August after determining that Moscow was violating the treaty, an accusation the Kremlin has denied.

The test comes amid growing uncertainty about the future of arms control. The last remaining treaty limitation on U.S. and Russian nuclear weapons — the New Start treaty of 2010 — is scheduled to expire in February 2021. That treaty can be extended for as long as five years without requiring a renegotiation of its main terms. The Trump administration has indicated little interest in doing so.

The Pentagon declined to reveal the maximum range of the missile tested. Last spring, when U.S. officials disclosed the testing plan, they said it would be roughly 1,860 miles to 2,480 miles (3,000 kilometers to 4,000 kilometers). That is sufficient to reach potential targets in parts of China from a base on Guam, for example. The Pentagon has made no basing decisions and has suggested that it will take at least a few years before such a missile would be ready for deployment.