A Russian weapon the U.S. is currently unable to defend against will be ready for war by 2020, according to sources with direct knowledge of American intelligence reports.
The sources, who spoke to CNBC on the condition of anonymity, said Russia successfully tested the weapon, which could carry a nuclear warhead, twice in 2016. The third known test of the device, called a hypersonic glide vehicle, was carried out in October 2017 and resulted in a failure when the platform crashed seconds before striking its target.
The latest revelations come more than two months after Russian President Vladimir Putin touted his nation's growing hypersonic arsenal as "invincible."
The hypersonic glide vehicle, dubbed Avangard, is designed to sit atop an intercontinental ballistic missile. Once launched, it uses aerodynamic forces to sail on top of the atmosphere.
One U.S. intelligence report, according to a source, noted that the hypersonic glide vehicles were mounted to Russian-made SS-19 intercontinental ballistic missiles — and one test featured a mock warhead.
While it is unclear whether Avangard will be outfitted with explosives, the precision and speed of the weapon is believed to pack enough force to obliterate targets.
The weapon, which Moscow has been developing for three decades, can travel at least five times the speed of sound, or about one mile per second.
"These kinds of boost glide vehicles attack the gaps in our missile defense system," Thomas Karako, director of the Missile Defense Project at the Center for Strategic and International Studies, told CNBC.
"There's no time like the present to modify our current missile defense posture," Karako added, saying it was "unfortunate that we have let Russia come this far."
The Russians are expected to conduct a fourth test sometime this summer.
Sources familiar with the U.S. intelligence reports assess that the Russian hypersonic glide vehicles are equipped with onboard countermeasures that are able to defeat even the most advanced missile-defense systems. The weapons are also highly maneuverable and, therefore, unpredictable, which makes them difficult to track.
The intelligence reports, which were curated this spring, calculate that Russia's hypersonic glide vehicles are likely to achieve initial operational capability by 2020, a significant step that would enable the Kremlin to surpass the U.S. and China in this regard.
During a state-of-the-nation address in March, Putin boasted about an arsenal of hypersonic nuclear weapons that he described as "invincible."
Putin claimed Avangard was capable of reaching targets at a speed of 20 times the speed of sound and strikes "like a fireball."
He also said that the hypersonic warhead had already entered serial production.
"I want to tell all those who have fueled 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," Putin said.
Putin added that the new capabilities were "not a bluff."
In an effort to back his bellicose rhetoric, Putin spoke in front of a projection showing video clips of the weapons as well as a simulated strike on the U.S. homeland.
America's top nuclear commander told lawmakers in March that U.S. forces are unable to shield against a hypersonic weapon.
"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. "Both Russia and China are aggressively pursuing hypersonic capabilities," he added, noting that the U.S. has "watched them test those capabilities."
Hyten, who has previously called Russia the "most significant threat" to the U.S., emphasized the need for the U.S. to add another type of nuclear weapon to its arsenal.
"I strongly agree with the need for a low-yield nuclear weapon," he said of the Pentagon's request for a low-yield warhead for submarine-launched ballistic missiles.
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 sufficient means to combat hypersonics.
President Donald Trump touted the defense-friendly spending bill as a "matter of national security" and highlighted not only big-ticket defense procurements but also the significant increase in missile defense funding.
However, even the $11.5 billion allocated for the Missile Defense Agency, the largest amount ever, may not be enough to fully modernize U.S. missile defense systems.
Karako said the funding is a step in the right direction but emphasized that the U.S. must field systems in space and integrate them with land- and sea-based platforms in order to counter the full spectrum of missile threats.
"The thing that is missing from the FY18 omnibus and the FY19 request is space sensors," Karako said in a prior interview with CNBC. "So tick tock, people, time is running out. The time for studies is over. Where is the plan to actually field some space sensors?"
Karako added that the missile-rich threat environment is getting more powerful and will put U.S. forces at risk.