The US appears to have rejected draft proposals by Germany for G8 members to agree tough measures in greenhouse gas emissions, leaked documents have shown.
Developing economies are at major risk from climate change
Wide-ranging US amendments to a draft communique prepared ahead of June's G8 in Germany summit cite a "fundamental opposition" to the proposals.
Germany wants all G8 members to agree timetables and targets for major cuts.
Greenpeace, who leaked the document, said it showed UK PM Tony Blair failed to persuade the US to alter its stance.
In the document, US officials make major changes to the communique.
In comments printed in red ink, the US negotiators express disappointment that earlier concerns have not been taken on board.
The changes strike out entire sentences and significantly reduce the certainty with which the statement addresses climate change.
"The US still has serious, fundamental concerns about this draft statement," a red-inked note reads.
"The treatment of climate change runs counter to our overall position and crosses 'multiple red lines' in terms of what we simply cannot agree to," it continues.
"We have tried to 'tread lightly' but there is only so far we can go given our fundamental opposition to the German position."
However, in Washington, senior US lawmakers have written to President Bush expressing their dismay at the administration's position, the AFP news agency reports.
Correspondents say the document hints at a looming struggle over the issue of climate change at the G8 summit, to be held on 6-8 June in Heiligendamm, Germany.
Chancellor Angela Merkel wants to use Germany's presidency of the G8 to secure a major climate change deal, including:
- Agreement to slow the rise in average temperatures this century to 2C
- A cut in global emissions by 50% below 1990 levels by 2050
- A rise in energy efficiency in power and transport by 20% by 2020.
Greenpeace Director John Sauven described the US position as "criminal".
"The US administration is clearly ignoring the global scientific consensus as well the groundswell of concern about climate change in the United States," he said.
Mrs Merkel should make it clear the US was isolated on the issue among G8 members, he added.
Speaking on 24 May, British Prime Minister Tony Blair suggested the US could be on the verge of altering its climate policy.
The US has not ratified the Kyoto Protocol, which sets out targets for lowering emissions until 2012.
"I can't think that there's going to be many people running for presidential office next time round in the US who aren't going to have climate change in their programme," said Mr Blair.
"I think it is possible that we will see action - and at least the beginnings of that action at the G8 - I hope so. That's what I'm arguing for."