Tony Blair told an international audience of politicians and business leaders tonight that he saw an evolution in US foreign policy towards a more consensual attitude which recognised that no country was powerful enough to go it alone in tackling global issues such as terrorism.

The Prime Minister's speech at the World Economic Forum had been billed as a setting-out of the UK's priorities as it takes over the presidency of the G8 club of industrialised nations, especially on the issues of climate change and eliminating poverty in Africa.

But Mr Blair spent a large part of it fending President Bush's inaugural speech last week, which he said pointed to a new era in which, he said, "the hard head has led to the warm heart".

Mr Blair conceded that the international atmosphere was less benign than when he last addressed the Davos meeting in 2000, although he said that it made both the issues and divisions clearer. But he said that the unity of the international response to the Asian tsunami on Boxing Day "showed an abundance of the human sentiment of solidarity".

"But there is a more fundamental political reason for optimism," Mr Blair added. "We may disagree about the nature of the problems and how to solve them, but no nation, however powerful, seriously believes that these problems can be resolved alone. Interdependence is no longer disputed.

"President Bush's inaguration speech last week marks a consistent evolution of US policy. He spoke of America's mission to bring freedom in place of tyranny to the world. Leave aside for a moment the odd insistence by some commentators that such a plea is evidence of the 'neo-conservative' grip on Washington - I thought progressives were all in favour of freedom rather than tyranny.

"The underlying features of the speech seem to me to be these: America accepts that terrorism cannot be defeated by military might alone...This may be open to debate... but it emphatically puts defeating the causes of terrorism alongside defeating the terrorists.

"Secondly, by its very nature, such a mission cannot be accomplished alone. It is the very antithesis of isolationism: the very essence of international engagement. It requires long-term co-operation."

After his appeal for international understanding of the Bush administration, Mr Blair then tried to win Washington's backing for measures to tackle global warming, insisting that they did not have to lead to "drastic" cuts in living standards. Washington has refused to sign up to the Kyoto Treaty setting international targets for the reduction of greenhouse gas emissions.

Despite a large snowfall on the Swiss ski resort over the past 24 hours that prevented President Chirac of France attending the event, Mr Blair said that a consensus was emerging on the existence and effects of global warming.

But at the same time he warned that governments could not be expected to push through changes that would seriously damage their economic prospects. "If we put forward as a solution to climate change something that involves drastic cuts in growth or standards of living, it matters not how justified it is, it simply won’t be agreed to," he said.

Those words might alarm environmentalists keen to see Britain follow through on the promise to use its G8 presidency to tackle climate change, but Mr Blair said the G8 had to set a "direction of travel" on global warming. The eight countries - Britain, the United States, France, Germany, Japan, Italy, Canada and Russia - represent 65 per cent of global economic output and 47 per cent of global CO2 emissions.

"I support the Kyoto Protocol. Others will not and that position is understood. But business and the global economy need to know that this is not an issue that is going away," Mr Blair said. "My clear view, for what it is worth, is that that debate will be how and on what timescale it is confronted: not whether."

Mr Blair also promised that Britain would dedicated itself during its G8 presidency to the issue of Africa. Although he made no explicit mention of Gordon Brown's new "Marshall Plan" for the continent, he spelled out his support for its key components - 100-per cent debt relief, a doubling of aid and a rewriting of world trade rules to encourage exports from the continent.

And he said that he would urge G8 leaders to accept and act on the report of the Africa Commission, set up by Mr Blair himself to suggest solutions to Africa's long-term problems, when they meet at Gleneagles in July.