Russia has tested a new nuclear-powered cruise missile capable of confusing existing defenses, moving closer to deploying it in its military, President Vladimir Putin said in remarks published Sunday.

The announcement, which followed years of testing of the Burevestnik missile, comes as part of the nuclear message from the Kremlin, which has resisted Western pressure for a ceasefire in Ukraine and strongly warned the United States and other NATO allies against sanctioning attacks inside Russia with longer-range Western weapons.

A video released by the Kremlin showed Putin, dressed in camouflage, receiving a briefing from Gen. Valery Gerasimov, Russia’s chief of staff, who told the Russian leader that the Burevestnik covered 14,000 kilometers (8,700 miles) in a key test on Tuesday.

Gerasimov said the Burevestnik, or storm petrel in Russian, spent 15 hours in the air, adding that “that’s not the limit.”

Little is known about the Burevestnik, codenamed Skyfall by NATO, and many Western experts have been skeptical about it, noting that a nuclear engine could be very unreliable.

WhenPutin revealed for the first timeWhen Russia was working on the weapon in its 2018 State of the Union address, it claimed it would have unlimited range, allowing it to circle the globe without being detected by missile defense systems.

Many observers argue that such a missile could be difficult to handle and pose an environmental threat. The United States and the Soviet Union worked on nuclear-powered missiles during the Cold War, but eventually shelved the projects as too dangerous.

The burevestniksupposedly suffered an explosionin August 2019 during tests at a Navy firing range in the White Sea, killing five nuclear engineers and two service members and causing a brief spike in radioactivity that fueled fears in a nearby city.

Russian officials never identified the weapon involved, but the United States said it was the Burevestnik.

“We need to determine the possible uses and start preparing the infrastructure to deploy these weapons in our armed forces,” Putin told Gerasimov.

The Russian leader also claimed that it was invulnerable to current and future anti-missile defenses, due to its almost unlimited range and unpredictable flight path.

Kirill Dmitriev, a senior Putin adviser who was in the United States when the video emerged, said his delegation informed their American colleagues about the “successful tests” of the Burevestnik, which he said was an “absolutely new class” of weapon.

Earlier this week, Putin led exercises by Russia’s strategic nuclear forces that included missile launch practices. The exercise came as a planned summit on Ukraine with US President Trump was put on hold.

The Kremlin said the drills involved all sides of Moscow’s nuclear triad, including intercontinental ballistic missiles that were test-launched from launch facilities in northwest Russia and a submarine in the Barents Sea. Tu-95 strategic bombers also participated in the exercises, firing long-range cruise missiles.

The exercise tested the capabilities of military command structures, the Kremlin said in a statement on Wednesday.