America's top nuclear commander described a grim scenario for U.S. forces facing off against a new breed of high-speed weapons that Russia and China are developing. "We don't have any defense that could deny the employment of such a weapon against us," Air Force Gen. John Hyten, commander of U.S. Strategic Command, told the Senate Armed Services Committee on Tuesday. This means that, as of now, the U.S. has to rely on deterrence against these so-called hypersonic weapons, he said.

U.S. Air Force General John Hyten, Commander of U.S. Strategic Command, testifies in a Senate Armed Services Committee hearing on Capitol Hill in Washington. Yuri Gripas | Reuters

Sen. Jim Inhofe, R-Okla., then asked the general to explain what a hypersonic weapon is and what it does. "A hypersonic threat is a system that starts out ballistic, so you'll see it like a ballistic missile, but then it depresses the trajectory and flies more like a cruise missile or airplane," Hyten said. "It goes up into the lower reaches of space and turns immediately back down and then levels out." At that point, Hyten said, the weapon will fly at very high speed, which is where the term hypersonic comes from. "Both Russia and China are aggressively pursuing hypersonic capabilities," Hyten told Inhofe. "We've watched them test those capabilities." While the Defense Department's latest budget request of $686 billion emphasizes a plan to offset emerging threats from Russia and China, it is clear that the U.S. lacks the means to combat hypersonics.

Chinese President Xi Jinping speaks with Russian President Vladimir Putin as leaders gather for a family photo during the Belt and Road Forum on Yanqi Lake, outside Beijing, China, May 15, 2017. Damir Sagolj | Reuters