Military posturing and increasingly hostile rhetoric between Russia and the West are raising the risk of an accidental slide towards a wider conflict that neither nuclear-armed side wants, experts warn.

Within days of reports that the United States was poised to send heavy military equipment to eastern Europe and the Baltic states, Russia retorted by announcing it planned to add 40 intercontinental nuclear missiles to its arsenal.

It was the latest in a string of threats and confrontations that have included Russian aircraft buzzing a US destroyer and British fighter jets scrambling after two Russian military aircraft flew near UK airspace.

The bellicose talk on both sides has raised speculation that Russia and the West are involved in a Cold War-style arms race, yet it also presents a more imminent danger: an accidental clash, experts said.

"I think it is seriously dangerous. There is a genuine misreading of the other side's intentions, I think on both sides, but especially from Russia," said Kadri Liik, a Russia expert at the European Council on Foreign Relations.

"There is a real danger that Russia will respond to an attack that happens only in its own head. They would retaliate in the real world."

Liik is among the experts who have called for direct "military-to-military" communication channels between Russia and Western-allied forces to keep any unintended clashes from "escalating into something more."

- 'Dramatically bad' -

Relations between Western powers and Moscow have plummeted to their lowest point since the depths of the Cold War over the Russian annexation of Crimea and its political backing for separatist rebels in eastern Ukraine.

For Jeffrey Mankoff, a fellow at the Center for Strategic and International Studies in Washington, the tension raises the possibility for miscalculation and accidents.

"But I don't think anybody on either side wants that," he said.

Instead the West's stance is intended to send "a message about resolve that is aimed both at the Eastern European states and Moscow."

What concerns him is the talk from some Russian analysts about limited use of nuclear weapons on the battlefield as well as President Vladimir Putin's recent reminders that Moscow is a nuclear power.

Yet he believes the West and Russia are well aware of the stakes in escalating to the point of fighting.

"Both sides understand that if it gets to a military confrontation, both sides have nuclear weapons and the consequences could be dramatically bad for everybody."

- 'We are serious' -

From a Russian perspective, the West's involvement in a region that used to be under Soviet sway is not innocent, experts said. In fact in Moscow's view, it was the West that fomented the uprising that forced Ukraine's pro-Russian president from power last year.

Accordingly, Putin's announcement about adding to Russia's nuclear missile arsenal was a logical response to the American plans to send heavy military equipment to Eastern Europe, said Dmitry Orlov, the pro-Kremlin director of the Agency for Political and Economic Communications.

He said Russia was obliged to respond to a threat from the United States, but it is not trying to pick a fight. Still, Orlov said there would not be a direct military confrontation.

"This is swordplay, a mutual exchange of rebukes," he said.

There are those, however, who think the real risk is in not responding to Russia's actions and rhetoric.

The West's lack of military action in Ukraine has only empowered Russia and given it an opportunity to pick up momentum, said Igor Sutyagin, a researcher at the Royal United Services Institute, a think-tank.

"They (Russians) are like water. If they see a gap they go forward, if they see concrete they just stop," said Sutyagin.

"America is just telling them, 'We are serious'," he added. "On a psychological level that reduces the risk of confrontation and clash."

Besides, he noted: "Last year Russia bought 38 new ICBMs, this year it will be 40. What is fundamentally different between these two situations? Nothing."

On top of that, Putin's "going to retire 72 (ICBMs)," said the researcher.