The first United Nations climate conference since the Kyoto agreement came into force in February has opened with the US still resisting targets.
Delegates meeting in the Canadian city of Montreal are to discuss how targets on cutting greenhouse gas emissions over the next seven years will be met.
Thousands of scientists, officials and environmentalists are attending 12 days of talks.
They will also look at what measures will follow in 2012 when Kyoto expires.
As host government, Canada is trying to find a formula which would enable the US, other industrialised countries and the developing nations to unite under a combined statement on future action.
A no-confidence vote due to be held in Canada later on Monday may disrupt proceedings as the minority Liberal government looks set to lose, and its defeat would trigger an election campaign.
The US, which fears the Kyoto deal could harm development and economic growth, has in any case said it would resist the Canadian proposal.
President Bush’s chief environmental advisor, James Connaughton, made clear the US would not support binding targets.
“We don’t need them,” he told reporters, pushing the case that “many of the more consequential initiatives [on cutting emissions] have occurred outside of a treaty process.”
Because the US has not ratified Kyoto, it will take no formal part in discussions held under its provisions.
However, the Americans do have a place at the table in Montreal, because they are participants in the UN Framework Convention on Climate Change – the broader agreement which gave rise to the legally binding protocol.
Canadian Environment Minister Stephane Dion told the BBC he was interested in seeking a rapprochement amongst countries with different views on the best approach to tackling climate change.
Developing countries’ share
Environmental pressure groups argue it is pointless to attempt to re-engage the Bush administration on meaningful worldwide action on global warming.
“The one thing… we cannot afford is to allow this US administration to hold the rest of the world hostage while they go on about voluntary this and voluntary that,” Steve Sawyer of Greenpeace told the BBC.
UK government officials, negotiating on behalf of the EU as Britain holds the current presidency, are determined to use the Montreal talks to demonstrate that binding targets on cutting greenhouse gas emissions are here to stay.
They also believe flexibility will be needed in the measures developing countries may be persuaded to adopt to limit the growth in their own emissions as their economies expand.
That is an extremely sensitive subject, our correspondent says.
A key measure of the success or otherwise of this conference will be if the first tentative signs emerge that countries such as China, India and Brazil are prepared even to talk about taking on formal commitments of their own in the global battle against climate change.