Russian President Vladimir Putin (R) shakes hands with his Chinese counterpart Xi Jinping during a signing ceremony following the talks at the Kremlin in Moscow, Russia July 4, 2017.

HUNTSVILLE, Ala. — America's top nuclear commander warned Tuesday that Russia and China are not "our friends" as Moscow and Beijing sprint to develop hypersonic weapons, a threat the United States currently cannot defend against.

"You can't call them [Russia and China] our friends if they're building weapons that can destroy the United States of America and, therefore, we have to develop the capability to respond," Air Force Gen. John Hyten, commander of U.S. Strategic Command said at the Space and Missile Defense Symposium in Huntsville, Alabama.

Hyten added that the Pentagon has nearly a dozen programs tasked with developing and defending against the new breed of weapons.

"I always wish we started [working on hypersonics] five years ago or 10 years ago because then we wouldn't be worried ... but we didn't so we have to step up now, and we are," he said.

The Pentagon awarded Lockheed Martin a $928 million U.S. Air Force contract in April for an undefined number of hypersonic strike weapons. Per the multimillion-dollar contract, Lockheed will be responsible for designing, engineering, weapon integration and logistical support.

Read more: Russia and China are 'aggressively developing' hypersonic weapons — here's what they are and why the US can't defend against them

A hypersonic weapon is a missile that travels at Mach 5 or higher, which is at least five times faster than the speed of sound. That means a hypersonic weapon can travel about one mile per second.

Hyten's warning also comes as the U.S. is embroiled in an escalating trade conflict with China and as the national security community warns that Russia is continuing to attack America's elections.

Hyten, who has previously called Russia the "most significant threat" to the U.S., recently described a grim scenario for American forces facing off against hypersonic weapons earlier this year.