Russian military leaders have recently had discussions about when and how Moscow might use tactical nuclear weapons in Ukraine, raising concerns in Washington and allied capitals, according to multiple senior officials.
This is reported by the New York Times.
President Vladimir Putin did not participate in the talks, which took place against the backdrop of Russia's increased nuclear rhetoric and its failures on the battlefield.
But the fact that senior Russian military leaders were even participating in the discussions worried the Biden administration because it showed how frustrated Russian generals are with their failures on the ground and suggests that Putin's veiled threats to use nuclear weapons may be more than just words.
But U.S. officials said they have yet to see any evidence that the Russians are moving nuclear weapons or taking other tactical steps to prepare for a strike.
Intelligence about these conversations was shared within the US government in mid-October.
American officials did not describe the scenarios considered by the military leadership for the use of nuclear weapons. However, William Burns, director of the CIA, has previously said that Putin's "potential desperation" after failing in the war could push Russia to use nuclear weapons.
John Kirby, a spokesman for the US National Security Council, declined to comment on "the details of this report."
"We have made it clear from the outset that Russia's comments regarding the potential use of nuclear weapons are deeply troubling and we take them seriously. We continue to monitor everything closely and see no signs that Russia is preparing for such a use," - Kirby said.
According to Pentagon estimates, Russia has up to 2,000 tactical nuclear weapons, which are intended for use on battlefields to suppress conventional armed forces. No tactical nuclear weapon has ever been used in combat, but it can be deployed by any means, including rockets or artillery shells.
Tactical nuclear weapons have less power and are designed for use at shorter distances than ICBM warheads.
Military experts say that the use of nuclear weapons - for the first time in 75 years - would fundamentally change the shape of war. Although the resulting destruction will depend on many factors, including the size of the weapon and the wind, even a small nuclear explosion could kill thousands of people and render parts of Ukraine uninhabitable.