“Just one launch, Boris, and England is gone,” said a broadcaster on Russian state television earlier this week, standing in front of a simulation of Britain and Ireland being wiped out by a nuclear weapon.

The alarming clip, which was circulated widely on social media, was swiftly criticised in the west as hyperbolic and provocative.

It was the latest instance of escalating Russian rhetoric over the possibility that Moscow could deploy nuclear weapons in retaliation for the west’s support for Ukraine. In February, Russia’s president Vladimir Putin unnerved the world when he put his nuclear forces on high alert, a move that signalled an apparent readiness to deploy them.

Last week, foreign minister Sergei Lavrov said in an interview with Russian state television: “The danger [of a Russian nuclear strike] is serious, real. And we must not underestimate it.”

Despite the sabre-rattling, not to mention Russia’s possession of the world’s largest nuclear arsenal, hardly any western intelligence officials or analysts think Moscow would carry out the kind of cataclysmic strike depicted by the broadcaster this week. The real question is whether Putin might resort to using smaller so-called tactical nuclear weapons to gain an advantage on the battlefield in Ukraine.

“Given the potential desperation of President Putin and the Russian leadership, given the setbacks that they’ve faced so far militarily, none of us can take lightly the threat posed by a potential resort to tactical nuclear weapons or low-yield nuclear weapons,” said CIA director Bill Burns last month.

But he added that “so far we haven’t seen a lot of practical evidence of the kind of deployments or military dispositions that would reinforce that concern”.

Western officials and analysts say they believe Russia has assessed the cost of using nuclear weapons of any kind to be prohibitively high, and is instead posturing to deter the US and its allies from becoming more involved in the war in Ukraine.

“Their hands are full with what is happening in the Donbas, they really don’t have any forces or time to deal with an expansion of the conflict with Nato or an escalation of the conflict because they know we will push back very strongly,” a European official said.

Leonor Tomero, who served as the top Pentagon official for nuclear policy in the first year of the Biden administration, said Russia’s use of a tactical nuclear weapon in Ukraine would “galvanise the whole world” against Russia. If it targeted civilians, there would be a “strong push” for the US to intervene militarily, she added.

“We don’t want them to miscalculate,” Tomero said. “We should make clear that it would have devastating consequences.”

As western fears over the threat of a Russian nuclear strike have dissipated somewhat, the US and allies have increased lethal assistance to Kyiv with less fear of retribution from Moscow and have started sending heavier weaponry to Ukraine in recent weeks.

In February, the Biden administration tasked a group called the Tiger Team with making contingency plans for possible escalation risks, such as the use of chemical, biological or nuclear weapons, a US official said. Since the start of the Ukraine conflict, Washington has not changed its nuclear posture or alert levels for America or its allies, officials said.

However officials warn Russia may escalate its tactics in other ways before it considers turning to nuclear weapons.

“We obviously have to be on guard for the potential use of chemical or biological weapons,” said Adam Schiff, the Democratic chair of the House intelligence committee, who returned this week from a trip to Kyiv.

“We have to keep a close eye on the Russian nuclear force posture and make sure that our intelligence agencies are trained on this target set so that if anything changes, we get a heads-up,” he added.

US officials and analysts have also not ruled out the possibility that Russia could eventually use short- and medium-range nuclear weapons able to reach Ukraine, as its military suffers setbacks and the depletion of its conventional forces in the conflict.

“They haven’t invested in a diverse arsenal of theatre nuclear weapons out of boredom. It will come down to a cost-benefit calculation by the Russians,” said Rebeccah Heinrichs, a nuclear expert at the Hudson Institute.

“The focus right now must be on signalling to the Russians that the cost would be much higher than anything they think they would benefit from if they used a nuclear weapon of any yield, even if in a big empty field,” she added.

While American officials want Moscow to know that there would be severe consequences for using nuclear weapons, part of the strategy of deterrence is paradoxically to avoid signalling exactly what the costs would be, said Scott Sagan, a political-science professor at Stanford University who was a senior Pentagon official.

The Biden administration’s most recent nuclear posture review, yet to be made public, maintains the US policy that nuclear weapons would only be used to deter or respond to a nuclear attack on the US or its allies.

“There’s a lot of planning and thinking going on behind the scenes,” Sagan said.

“People are not just trying to think in the old cold war-style of a tit for tat,” he added. “They’re trying to think of what could we do that could signal to the Russians that this is unacceptable and exceedingly dangerous, but do so in a way that doesn’t cause automatic escalation.”