If the US Administration didn’t have enough to worry about, given the current state of the world, it spent much of the weekend wondering whether Moscow had declared another Cold War.

On Saturday President Putin delivered the most aggressive verbal assault on the US and its European allies that a Russian leader has uttered since the Cold War ended 16 years ago. In a speech to the annual Munich Security Conference that evoked memories of the days when the two superpowers threatened to wipe each other and much of the world off the map, Mr Putin attacked what he called the “illegitimate” US foreign policy of the past few years.

In unusually brusque and undiplomatic language, he said the US had “overstepped its boundaries in every sphere”, had fuelled a new nuclear arms race and was aggressively destabilising the Middle East.

This was more than just another familiar, if blunt, recitation of the supposed crimes of the Bush Administration. Speaking to an audience that included European leaders and Angela Merkel, the German Chancellor, as well as Americans, Mr Putin attacked Nato. He said the inclusion of former Soviet satellite states in the Atlantic alliance had destabilised Europe and threatened Russia. “Against whom is this expansion directed?” he asked. Not since Nikita Khrushchev banged his shoe on the table at the United Nations in 1960 has an international gathering heard such an icy blast from Moscow’s leadership.

US officials were careful to play down the unsettling new Russian tone. Robert Gates, the US Defence Secretary, speaking at the conference yesterday, gently mocked Mr Putin’s performance, saying that it “almost filled me with nostalgia for a less complex time. Almost”. In fact he went out of his way to sound a strikingly emollient tone, admitting US mistakes in the last few years. For a century, he said, the US had enjoyed a reputation of being a force for good in the world but he acknowledged that some of that had been lost in recent years and that the US had work to do to repair its reputation.

John McCain, the Arizona senator and leading contender for the Republican nomination in next year’s presidential election, who has been unsparing in his criticism of Mr Putin’s authoritarian tendencies in the past, was restrained, merely taking issue with Mr Putin’s characterisation of the modern world as a “unipolar” one. US officials noted pointedly that it was Europeans, including some leaders of the eastern European countries that used to live under the Russian heel, who were present at the weekend conference, who were most angered by Moscow’s new tone. German government officials were privately furious with the Russian leader’s remarks.

Coming as it did on German soil, just minutes after Chancellor Merkel had given a warm diplomatic overview of transatlantic relations, Mr Putin’s speech was considered a breach of the normal diplomatic protocols. It was more than discourteous, however. The Munich conference, the most important annual transatlantic security policy forum, originated in the darkest days of the Cold War.

Chancellor Merkel, who lived under Soviet domination of eastern Europe as an East German citizen in the 1980s, is under no illusions about the political instincts of Mr Putin, the former KGB agent. But she and her aides had not imagined that the Russian leader would deliver such a blunt attack in the midst of her efforts to improve relations among European countries and were puzzled by the tone. US officials believe the speech was intended to represent Russia as a muscular new power in the world, after its long decline and humiliation since Cold War days. Bolstered by increased energy prices in the past five years, a continuing healthy economic expansion and signs that its old adversary in Washington has run into serious global trouble, the Russian leadership seems eager to show that it is back as an actor on the world stage.

The sudden apparent deterioration in US-Russian relations, especially with a man of whom President Bush has spoken so warmly, did not seem to alarm Americans, however.

The Munich event has been dominated for the past few years by transatlantic splits as the US found itself under attack from its old allies over the war in Iraq. Throughout that time, Donald Rumsfeld, the former defence secretary, played the role of principal villain at the conference.

This year Europeans were presented with a new villain, and perhaps in the process were reminded that, for all its faults, America may not after all really be the most threatening nation on earth.

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