Russia tested a new nuclear-capable and powered cruise missile fit to confound existing defenses, inching closer to deploying it to its military, President Vladimir Putin said in remarks released on Sunday.

The announcement, which followed years of tests of the Burevestnik missile, comes as part of nuclear messaging from the Kremlin, which has resisted Western pressure for a ceasefire in Ukraine and strongly warned the U.S. and other NATO allies against sanctioning strikes deep inside Russia with longer-range Western weapons.

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

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

Little is known about the Burevestnik, which was code-named Skyfall by NATO, and many Western experts have been skeptical about it, noting that a nuclear engine could be highly unreliable.

When Putin first revealed that Russia was working on the weapon in his 2018 state-of-the-nation address, he claimed it would have an unlimited range, allowing it to circle the globe undetected by missile defense systems.

Many observers argue that such a missile could be difficult to handle and pose an environmental threat. The U.S. and the Soviet Union worked on nuclear-powered missiles during the Cold War, but they eventually shelved the projects, considering them too hazardous.

The Burevestnik reportedly suffered an explosion in August 2019 during tests at a navy range on the White Sea, killing five nuclear engineers and two service members and resulting in a brief spike in radioactivity that fueled fears in a nearby city.

Russian officials never identified the weapon involved, but the U.S. said it was the Burevestnik.

"We need to determine the possible uses and begin preparing the infrastructure for deploying these weapons to our armed forces," Putin told Gerasimov.

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

Kirill Dmitriev, a top Putin aide who was in the U.S. as the video surfaced, said his delegation informed U.S. colleagues of the "successful testing" of the Burevestnik, which he said was an "absolutely new class" of weapon.

Earlier this week, Putin directed drills of Russia's strategic nuclear forces that featured practice missile launches. The exercise came as his planned summit on Ukraine with U.S. President Trump was put on hold.

The Kremlin said that the maneuvers involved all parts of Moscow's nuclear triad, including intercontinental ballistic missiles that were test-fired from launch facilities in northwestern Russia and a submarine in the Barents Sea. The drills also involved Tu-95 strategic bombers firing long-range cruise missiles.

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