'If there is a rifle hanging on the wall in the first act, in the third act, the rifle will be fired." KGB defector Oleg Gordievsky is musing on the words of the Russian dramatist Chekhov, as he considers Vladimir Putin's latest strategic moves, which he fears could lead inevitably to all-out military conflict.

"When Putin came to power, it was clear what was going to happen," says Mr Gordievsky of his former KGB colleague. "I warned John Scarlett [Gordievsky's former handler in Moscow who now heads MI6], I warned the Foreign Office, I warned journalists. Now they believe me," he thunders.

Not content with hanging up a rifle on the wall, the Russian president has lined up a whole array of weaponry, including nuclear-capable strategic bombers while ratcheting up his rhetoric, prompting talk of a "new Cold War".

"The old one never stopped," said Dan Plesch a senior British arms control analyst who shares the concern of the highest-ranking KGB officer to defect to the UK that we are sleepwalking to disaster. One false move, and "there is a very significant danger of global nuclear war", according to Mr Plesch.

In a week in which the world has been distracted by the bare muscular torso of the 54-year-old Russian leader on his Siberian holiday – compared with the air-brushed "love handles" of President Nicolas Sarkozy of France – one thing stands out in the series of images on the Kremlin website. This is a president who wears military fatigues, not jeans, in his spare time.

The Russian bear is back with a vengeance. But seen from Moscow, the Kremlin is simply reacting to a series of provocations by the United States and Nato as the Western alliance creeps towards Russian borders, threatening the security of the state.

The "new Cold War" has its origins in a speech made by Mr Putin last February at a security conference in Munich, in front of an audience of Western defence ministers and parliamentarians, in which he listed Moscow's grievances and accused the Bush administration of trying to establish a "unipolar" world.

"One single centre of power. One single centre of force. One single centre of decision-making. This is the world of one master, one sovereign," the President complained.

The speech went down a storm back home, where Russian newspapers congratulated the President for telling the West where to get off. But it kicked up a different kind of storm in the West, already worried about oil-rich Russia using energy as a weapon to bully its neighbours and concerned about the country's return to more authoritarian rule under Mr Putin.

Since the Munich speech, in which the Russian leader criticized American plans to base part of an anti-missile defence shield in Poland and the Czech Republic – both former Warsaw Pact nations – the chill wind has got chillier. The West and Russia are at loggerheads over a host of political issues, including Iran's nuclear ambitions, Iraq, the future of Kosovo and, in particular, Nato expansion – which is a Kremlin obsession.

British-Russian relations are at their worst in decades after the radiation poisoning of the former KGB agent, Alexander Litvinenko, in central London last November, and Russia's refusal to extradite the former KGB man who is suspected of the murder.

In May, Mr Putin fired off another volley against American unilateralism, obliquely comparing US policies to those of the Third Reich in a speech commemorating the 62nd anniversary of the fall of Nazi Germany.

In the same speech, he attacked Estonia, a new European Union member, for relocating a monument to the Red Army, which he said was "sowing discord and new distrust between states and people". When Estonian government websites fell victim to an unprecedented cyber attack, Nato was called in as the finger of suspicion fell on the Kremlin.

Things have got steadily worse: an EU-Russia summit held amid tensions between Russia and Poland and Estonia ended acrimoniously as the European leaders criticised the arrest of a group of Russian opposition activists led by Garry Kasparov. They were detained on their way to a protest rally near the summit in Samara. Then came Russia's threat to turn of gas supplies to Belarus, in what became almost a replay of the stand-off in 2006 when supplies to Ukraine were shut down, ostensibly to punish the former Soviet republic for its Orange Revolution.

But the military developments have clearly raised the most dangerous tensions between Russia and the West. In retaliation for the US anti-missile shield plans, Mr Putin announced that Russia would retarget its own missiles towards Europe to counter the proposed installations in its former satellite states that are now EU members and fervently pro-US. Alarm bells rang in Western capitals when on 14 July, Russia formally declared it was suspending participation in the Treaty on Conventional Armed Forces (CFE) in Europe, one of the pillars of East-West disarmament, dating from 1990.

On 6 August, according to the pro-Western Georgian government, a Russian warplane flew over the Caucasus mountains and fired a missile, which crashed into a Georgian potato field. Although the missile did not explode, the Georgians accused the Russians of violating their airspace and took their case to the UN security council. Georgia last week accused the Russians of a second violation. And on Friday, Georgia said its forces had fired on a Russian jet, which crashed into a forest.

Then, on 17 August, President Putin announced that 20 strategic bombers had been sent far over the Atlantic, Pacific and Arctic oceans – in a concrete demonstration of Moscow's muscular new posture. On the same day, Britain's Ministry of Defence announced that two RAF jets had shadowed a Russian bomber that approached British air space.

"What he is doing is not real yet, but could become real any day. Europe should be prepared," said Mr Gordievsky. Yet while European analysts warn that the tense situation could deteriorate into an armed conflict in the time it would take President Putin to remove his shirt, they also point out that Russia should not be the only one blamed for the "new Cold War."

Mr Putin, in announcing the resumption of round-the-clock flights by long-range bombers with a nuclear capability, pointed out that other nations – in other words, the US – had continued their missions since the end of the Cold War.

"Washington failed to live up to its commitments to Russia," said Mr Plesch, director of the Centre for International Studies and Diplomacy at the School of Oriental and African Studies in London. The Bush administration pulled out of the anti-ballistic missile treaty, jeopardised the nuclear non-proliferation treaty, and the CFE treaty was never ratified by Nato. "The Americans are still flying round Russia," he said, adding that flights by American strategic bombers had remained at the same level since the Cold War.

Mr Plesch argues that Russia is right to feel threatened by the American anti-missile shield, which, according to the Bush administration, would target incoming missiles from North Korea or Iran. "Now the Americans believe they have a first strike against Russia with conventional weapons," he said.

According to the Prague-based Czech analyst Petr Kratochvil, Mr Putin's harsh rhetoric is part of a strategy directed towards his domestic audience in the approach to next year's presidential election, which is expected to be won by a close ally of the President, who is himself constitutionally barred from running for a third term.

In Mr Kratochvil's view, although relations with the West are "much worse than five years ago", armed conflict is not likely for the simple reason that Russia cannot compete as a superpower with America, either economically or militarily.

Mr Putin's nostalgia for the Soviet era – he has described the collapse of the Soviet Union as "the greatest geopolitical catastrophe" of the last century – is raised "because it resonates with the public", according to Mr Kratochvil. "I don't think he believes it himself. He's trying to make it less painful for people as Russia becomes a regional power."

So what's to be done? Despite the tensions, there is a sense on both sides of the Atlantic that the US and Russia are looking for a way out. The US Secretary of State, Condoleezza Rice, herself a Soviet scholar, and Russia's hawkish First Deputy Prime Minister and former Defence Minister, Sergei Ivanov, have rejected suggestions of a new Cold War. And despite all the bluster, Russia is still cooperating with Nato, having broken off all cooperation in 1999 during the Kosovo crisis.

During a hearing of the US House Armed Forces Subcommittee on Strategic Forces in Washington last month, the committee chairwoman, Ellen Tauscher, said they were looking for solutions. She added that the US was now "at a critical juncture regarding our strategic posture".

Mr Plesch said it was time to revive the ideal of Presidents Reagan and Gorbachev at their doomed Reykjavik summit, at which they pledged to eliminate the US and Soviet nuclear arsenals. He is not alone. None other than Henry Kissinger has signed up to the goal of nuclear disarmament.

"If you say 'save the whale' or 'do this to stop global warming', everyone agrees. But if you say general and complete disarmament, people look at you as if you've completely lost the plot," Mr Plesch said.

But amid the attempts to move back to a disarmament agenda, there is a key ingredient missing. "Trust but verify," President Reagan used to say to President Gorbachev after they signed a landmark agreement eliminating both sides' intermediate-range missiles. What will complicate the efforts to end the "new Cold War" is that trust has now disappeared in the relationship between the West and President Putin's Russia.