Air Force General John Hyten said the weapons travel into the low reaches of space before returning to Earth at an incredibly high speed.
He said: “Both Russia and China are aggressively pursuing hypersonic capabilities. We’ve watched them test those capabilities.
“We don’t have any defence that could deny the employment of such a weapon against us.”
He said the US needed to add another nuclear weapon to its arsenal in a bid to protect itself from a possible attack and said this was the only sort of “deterrent” Russia would understand.
Gen. Hyten said: “I strongly agree with the need for a low-yield nuclear weapon. That capability is a deterrence weapon to respond to the threat that Russia, in particular, is portraying.
“President Putin announced as far back as April of 2000 that the Russian doctrine will be to use a low-yield nuclear weapon on the battlefield.”
It comes after the Russian President revealed a terrifying new weapon.
During his state of the union speech earlier this month, Mr Putin boasted his new military toy would render opposition defence systems “useless”.
He said: “I want to tell all those who have fuelled the arms race over the last 15 years, sought to win unilateral advantages over Russia, introduced unlawful sanctions aimed to contain our country’s development: you have failed to contain Russia.
“The West has ignored us. Nobody listened to us. Well listen to us now.”
He said the new ICBM is “powerful and modern”, adding “defence systems will not be able to withstand it, missile defences will be useless against it”.
In a dire warning which takes on an even graver importance following this week’s ratcheting-up of tension, Mr Putin said: “We have everything we need.
“Any kind of attack against Russia or its allies will be regarded as a nuclear attack against Russia and in response we will take action instantaneously no matter what the consequences are.
“Nobody should have any doubt about that.”