The French and Germans would prefer a 7-1 split over the final communiqué on the issue, which is being negotiated this weekend by officials in London, rather than bow to pressure by the US for it to be watered down.
A leaked draft of the communiqué yesterday showed that the Americans are still resisting a tough wording on the scientific evidence that human activity is causing climate change. British negotiators are seeking a compromise to keep the US on board, but France and Germany are insisting on an explicit reference to the scientific evidence, with wording on the urgency of the threat from global warming.
The US is seeking to remove a paragraph stating "climate change is a serious and long-term challenge that has the potential to affect every part of the globe". A reference in an earlier draft to a joint declaration in early June by top scientists from all G8 nations that human activities were a significant contributor to global warming has already been removed.
Another paragraph refers to a predicted 60 per cent growth in global energy demands over the next 25 years, but a section stating "we know that we need to slow, stop and then reverse the growth in greenhouse gases" is also under question.
"If anything this draft is weaker than the one that was on the table before," Jennifer Morgan, climate change expert at the World-Wildlife Fund said.
French negotiators are demanding the inclusion in the communiqué of an explicit reference to the Kyoto agreement, which the US has refused to sign. That could leave the US isolated.
A senior French diplomat said: "We are aware that the US has not signed up to Kyoto. This is a fact of life.
"We would like to see clear references to the Kyoto protocol in the communiqué. The EU has taken a very united stance on Kyoto. It was very influential in getting Russia to sign up."
Mr Blair hinted yesterday that he would try to sidestep the issue by seeking agreement with the US on future action. He said in a webchat on the G8: "We have had a disagreement with America over Kyoto. The question is, in 2012 can we put in place a new process that informs America and establishes a consensus for action involving both the developed world and the emerging economies like India and China? I hope the G8 can make progress here."
Downing Street signalled last night that Britain would resist being forced to join France and Germany in a 7-1 standoff against Mr Bush at the summit. A senior cabinet minister said Britain would adopt the role of honest brokers as hosts of the G8 conference.
The Prime Minister's official spokesman said: "We are approaching this as the president of the G8. Serious negotiations are going on."
However, President Chirac is determined to hold Mr Blair to the principles for climate change that the UK has set out in the past. "We are very supportive of the UK on the G8," said the French source. "We share the view with Blair that the two main topics of development aid and climate change are equally important and are linked.
"It is in Africa that the effects of climate change will be felt most. The two go hand in hand. It doesn't make sense to increase development aid if that effort is going to be wasted as a result of unchallenged climate change."
On the development issue, Gordon Brown will reinforce the commitment to cutting African debt in a speech today. Mr Blair said he would be wearing the "Make Poverty History'' white wrist band at the G8.
However, the charity Oxfam has warned that an attempt in the G8 to delay aid delivery from 2006 until 2010 would leave almost a $100bn (£56bn) gap that could see 55 million children die from poverty.
"There have been reports that the US is saying it will increase aid, but the delivery date will be delayed to 2010. Our figures show that if the aid were delivered next year, it would be nearly $100bn more," Oxfam said.
n Mr Blair will also push for a statement on the Middle East at the G8 Summit in an attempt to reinforce progress on the "road map" for Israel and Palestine.