Tony Blair has told the World Economic Forum a major breakthrough on long-term climate change goals could be close.
He told the forum in Davos, Switzerland it was possible because of a "quantum shift" in the attitude of the US.
He said the German G8 presidency offered an opportunity for a new international agreement for when the Kyoto Protocol expired in 2012.
"I believe we are potentially on the verge of a breakthrough," he said.
The UK prime minister praised Chancellor Angela Merkel's focus on climate change during her EU presidency and India and China's engagement with the G8.
He also pledged to work with other world leaders towards a more "radical" and "comprehensive" successor to the Kyoto protocol.
"The German G8 Presidency gives us the opportunity to agree at least the principles of a new, binding international agreement to come into effect when the Kyoto Protocol expires in 2012," Mr Blair said.
"But one which is more radical than Kyoto and more comprehensive, one which this time includes all the major countries of the world."
However, he said any agreement would not be able to deliver without binding commitments from the US, China and India.
He told the World Economic Forum: "If Britain shut down our emissions entirely, i.e. we closed down the country - not the legacy I want - the growth in China's emissions would make up the difference in just two years.
"Without the biggest economies being part of the framework to reduce carbon dependence, we have no earthly chance of success," he said.
But Mr Blair added: "The mood in the US is in the process of a quantum shift.
"The president's State of the Union address built on his 'addicted to oil' speech last year and set the first US targets for a reduction in petrol consumption."
In a wide-ranging speech on world issues, Mr Blair also said he believed nuclear power had to be part of the future.
"But I look ahead in my country and I see a situation where we're going to move, incidentally, from self-sufficiency in gas to importing 90% of it, and I say for reasons both of energy efficiency and reducing carbon emissions, how are we going to do that without nuclear energy being part of the mix?
"And I think we've got to get over this false view that it offers nothing by way of the future. I think there is a whole new generation of technology growing up around it," he said.
According to the BBC's Tim Weber, the conference hall was completely full for Mr Blair's speech.
Both his speech and following question and answer session received much applause and a standing ovation, our reporter in Davos said.
Some observers are seeing Mr Blair's speech as an attempt to be viewed as an elder statesman once he steps down as prime minister.
Trade ministers from around 30 countries have previously agreed during the conference that full-scale global trade talks should resume quickly.
Politicians have said it would be "catastrophic" if the talks failed.