US intelligence monitored the conversations, which did not involve Vladimir Putin, but caused unease in Washington in the wake of aggressive rhetoric from the Russian president.
John Kirby, the White House national security spokesman, said there was “no indication” that the Russian President had decided to use a nuclear weapon, but warned “we may not pick up every single indicator”.
He added: “It’s unsettling in terms of the degree to which he feels he has to stretch to prosecute this war.”
It came as Dmitry Medvedev, the former Russian president and senior security council official, said Ukraine’s objective to reclaim all its Russian-occupied territories, including the Donbas region and Crimea, would be a “threat to the existence of our state”.
Medvedev said that would be a “direct reason” to invoke Russia’s nuclear deterrence.
The Russian foreign ministry also claimed the world was teetering on the brink of nuclear conflict, and accused the West of provocation which could lead to “catastrophic consequences”.
In a statement the ministry denounced “irresponsible and impudent actions aimed at undermining our national security,” and called on other nuclear powers to “abandon dangerous attempts to infringe on each other’s vital interests”.
The statement called on nuclear powers - the US, UK, France and China - to “work together to solve the priority task” of “avoiding any military clash”.
Russia’s next scheduled presidential election is in 2024 but Vladimir Putin isn't expected to go without a fight. Photo / AP
Meanwhile, a senior Western official said Putin had been weakened by his decision to invade Ukraine.
The official said: “We are seeing the Russian military humbled by Ukraine. They didn’t have a Plan B, they thought this would be be easy.
”That has to mean people are talking more about succession.”
Russia’s next scheduled presidential election is in 2024. However, they added that new leadership in the Kremlin was not expected “anytime soon”.
Russia has up to 2000 tactical nuclear weapons, and any decision to use one would have to be taken by Putin. The intelligence that some of his military officials discussed how it would be done was first reported by the New York Times.
No specific targets were detailed in the discussions between the Russian military officials.
Since the intelligence became known in Washington in mid-October there have been communications between senior US and Russian figures. That has included calls between Lloyd Austin, the US Defence Secretary, and his Russian counterpart Sergei Shoigu.
Last night, Dmitry Peskov, Putin’s spokesman, called the New York Times report “very irresponsible”.
He said Moscow did “not have the slightest intention to take part in this”.
In Washington, Kirby said: “We’ve been clear from the outset that Russia’s comments about the potential use of nuclear weapons are concerning, and we take them seriously. We continue to monitor this as best we can.
”We’ve no indications that Mr Putin has made a decision to use nuclear weapons but this is deeply concerning.”
He added: “When you again hear Mr Putin talking about it, making historical references to Hiroshima and Nagasaki, we take note of that.”
Locals stand in line waiting for free bread from volunteers in Bakhmut, the site of the heaviest battle against the Russian troops in the Donetsk region, Ukraine, on October 28. Photo / AP
According to the British security think-tank Rusi, Russia’s tactical nuclear arsenal is limited in range to 300 miles (480km), compared to a 3000 mile (4830km) strategic nuclear missile.
But they still have immense destructive power, with some having a potential yield similar to the atomic bomb dropped on Hiroshima in 1945.
Analysts said Russia could choose to use a low-yield tactical nuclear weapon in an unpopulated area of Ukraine, causing no loss of life.
