Two US officials confirmed to Fox News on Thursday that a Russian “experimental intermediate-range ballistic missile” (IRBM) launched at Ukraine was not hypersonic.

Russian President Vladimir Putin confirmed the attack in an address to the nation on Thursday evening, saying it was in direct response to the US and Britain jointly approving Ukraine’s use of Western-supplied long-range missiles to attack Russia .

Putin and US sources have since confirmed that the attack was not an intercontinental ballistic missile (ICBM), but the Kremlin chief also claimed that the weapon used poses a significant challenge to Western countries.

Pentagon Deputy Press Secretary Sabrina Singh confirmed to reporters during a press conference on Thursday that Russia has launched an IRBM based on one of Russia’s ICBM models. She sometimes called the IRBM “experimental” and explained that this was the first time the missile had been used on the battlefield.

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A Yars intercontinental ballistic missile is tested from the Plesetsk launch pad in northwestern Russia. (Press service of the Russian Ministry of Defense via AP)

“This was a new type of lethal capability deployed on the battlefield, so that certainly concerns us,” Singh said.

She also said the US was briefly notified through nuclear or risk reduction channels before the launch.

Still, Singh told reporters that the Defense Department has not seen any change in Russia’s nuclear posture, nor has the US made any change in its own policies.

Putin said, according to a translation, that the missile attacked targets at a speed of Mach 10.

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Russian President Vladimir Putin listens to the Moscow-appointed head of Ukraine’s Russian-controlled Zaporizhia region, Yevgeny Balitsky, during a meeting at the Moscow Kremlin. (Vyacheslav Prokofyev, Sputnik, Kremlin Pool Photo via AP)

“That’s 4.0 kilometers per second,” Putin said. “The world’s current air defense systems and the missile defense systems developed by the Americans in Europe do not intercept such missiles.”

Despite Putin’s claim, two US defense officials told Fox News that the missile was not hypersonic, which has a speed of more than 5,000 km per hour and faster than Mach 5, according to NASA.

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Singh told reporters that the only escalation in the war between Russia and Ukraine is that Russia has invaded a sovereign border country and turned to North Korea to send about 11,000 soldiers to fight against Ukraine.

Following President Biden’s reversal of position this week to allow Ukraine to use US-supplied Long-Range Army Tactical Missile Systems (ATACMS) against the Russian homeland, Kiev immediately launched strikes against a military arsenal in the Russian region Bryansk, more than 110 kilometers from the Russian homeland. The border of Ukraine.

Ukrainian soldiers train in the Zaporizhia region. (Andriy Andriyenko/65th Mechanized Brigade of Ukraine via AP)

While Ukrainian forces officially fired the advanced missiles, the weapon system still relies on US satellites to reach its target, an issue Putin touched on in his unannounced speech on Thursday.

“We are testing the Oreshnik missile systems in combat conditions in response to the aggressive actions of NATO countries against Russia. We will decide on the further deployment of medium and shorter range missiles depending on the actions of the US and its satellites.” he said.

Putin claimed that Russia will warn Ukrainian citizens of an impending attack such as the one he carried out on Thursday, although it remains unclear whether he has issued a warning to Ukrainians living in Dnipro.

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The Kremlin chief said the “defense industry” was targeted, although images released by Ukraine’s defense ministry showed what appeared to be civilian infrastructure caught up in the fighting.

Fox News Digital’s Caitlin McFall contributed to this report.