Together the eight countries account for account for 65 per cent of the global economy and one third of the world's carbon dioxide (CO2) emissions.

Booming Asian economies are pumping out more and more CO2 [EPA]
But the Bush administration has shown little enthusiasm for any commitment to reduce emissions without similar action from China and India.

"I've always advocated that there needs to be a common understanding and that starts with a goal, Bush said.

"And I also am realistic enough to tell you that if China and India don't share that same aspiration, that we're not going to solve the problem.''

Yasuo Fukuda, the Japanese prime minister, who held talks with Bush on Sunday, is hoping to push leaders to pledge to halve emissions by the middle of the century.

A report last year by the Intergovernmental Panel on Climate Change (IPCC) – a UN network of 2,000 scientists – called on rich nations to reduce emissions by 25-40 per cent by 2020 to avoid the worst effects of global warming.

Without urgent action, they said climate change would trigger widespread drought, floods, higher sea levels and worsening storms.

Even a rise in temperature of just 2C could subject up to two billion people to water shortages by 2050 and threaten extinction for 20-30 per cent of the world's species, the IPCC said.