President Vladimir V. Putin of Russia, center, and his defense minister, Sergei K. Shoigu, second from left, on Thursday at the National Defense Control Center in Moscow where they watched a video of the launch of a hypersonic weapon.
Credit: Michael Klimentyev

WASHINGTON — The Russian military on Friday said it had deployed a hypersonic weapon that flies at superfast speeds and can easily evade American missile defense systems, potentially setting off a new chapter in the long arms race between the world’s pre-eminent nuclear powers.

American officials said Friday they have little doubt that the Russians have a working hypersonic weapon — which sits on top of a modified missile and is capable of carrying a nuclear warhead at speeds faster than 3,800 miles per hour.

Moscow has been working on the technology for years and has invested heavily in it, determined to reverse the pattern in the Cold War, when it was often struggling to catch up with American nuclear weapons systems. If the […]