The G8 leaders have promised a "new dialogue" on climate change.
The science is such that "we know enough to act now", the G8 says
Their communiqué, released at the end of the Gleneagles summit, states that global warming is a "serious long-term challenge" for the entire planet.
And the nations promised to act with "resolve and urgency" to reduce the gas emissions thought responsible - but they specified no targets or timetable.
Instead, the UK Prime Minister Tony Blair says the G8 countries will meet in November for further discussions.
Environmental action groups say they are pleased Mr Blair prioritised climate change but are disappointed at the outcome of the summit.
They say the communiqué represents "no significant movement", largely because the US administration has been unwilling to shift its position.
Lord May of Oxford, President of the UK's academy of science, the Royal Society, believes opening a dialogue on climate change is not nearly enough.
"At the heart of the communiqué is a disappointing failure by the leaders of the G8 unequivocally to recognise the urgency with which we must be addressing the global threat of climate change," he said.
"Make no mistake, the science already justifies reversing - not merely slowing - the global growth of greenhouse gas emissions. Further delays will make the G8's avowed commitment in this communiqué to avoid dangerous impacts of climate change extremely difficult.
"In its communiqué the G8 talks of 'facing a moment of opportunity' while, at the same time, turning away from that moment."
In a statement, Tony Blair acknowledged that the disagreement over Kyoto had not been resolved. But he said the most important thing was reaching a consensus, and that they had achieved.
"If it is impossible to bring America into the consensus.... we will never ensure that the huge emerging economies, particularly those of India and China ...are part of the dialogue," he said.
"If we can't have America as part of the dialogue, and we can't have India and China as part of the dialogue, there is no possibility in us succeeding in resolving this issue.
"What we have is a firm consensus that this problem needs to be tackled, has to be tackled now, together with a dialogue for the future. That, I think, is something to be proud of."
Mark Kenbar, of The Climate Group, believes that Tony Blair "gave it his best shot".
"We would congratulate the prime minister and we are sure he made every effort to achieve something more concrete," he told the BBC News website. "However, the result is not as much as we could have hoped for.
"I would say we have moved neither forwards nor backwards. There is at least one country that is not prepared to make emissions reductions. The Bush administration is just not prepared to go as far as others are."
COMMUNIQUÉ: MAIN POINTS
It describes climate change as a "serious long-term challenge"
It says human activities contribute "in large part" to increases in greenhouse gases
It says "we know enough to act now and put ourselves on a path to slow and, as science justifies, stop and then reverse the growth of greenhouse gases"
It says two billion people lack access to modern energy sources; increasing access is needed in order to support the Millennium Goals
It says that developed nations have the responsibility to act
Tony Juniper, of Friends of the Earth, agreed that the communiqué would have looked very different if it was not for the United States.
"The Bush administration has again done its best to derail international action to tackle climate change, but this is by no means the end," he said.
"Tony Blair was right to prioritise climate change at the G8. Even if there was no progress here, there has been a big impact on public awareness and that will make it easier to achieve more in future talks."
And John Lanchbery, head of climate change at the UK's Royal Society for the Protection of Birds, added: "The US was inevitably the sticking point; President Bush has refused to heed worldwide calls for measures to tackle climate change despite his own scientists and some Republican politicians demanding action, too."
The green lobby believes the other G8 nations have bowed to US pressure on climate change by approving a watered-down declaration that avoids any talk of concrete action.
President George W Bush has been reluctant to accept the position of the "scientific consensus" on global warming, and commentators were eager to see what form of words on the issue he would agree to in the communiqué.
It states that, "while uncertainty remains in our understanding of climate science, we know enough to act now".
Some see that as movement by the US president. The French leader, Jacques Chirac, said: "The agreement which has been reached - even if it doesn't go as far as France had hoped - has a great virtue, namely that it re-establishes vital dialogue and co-operation amongst the industrialised countries on the one hand - those which ratified Kyoto and those which didn't, in other words the US - and on the other between the industrialised countries and the developing countries.
"Everybody understands fully well that with the dangers confronting us, as far as climate is concerned, only a coherent plan of action has a chance of turning things around."
The Gleneagles communiqué is strong on helping developing countries build low-carbon economies. It recognises that their needs to achieve economic growth will require access to sustainable, clean energy.
It also states that the UN Framework on Climate Change - of which the Kyoto Protocol is the best-known part - is the "appropriate forum for negotiating the future of the multilateral regime on climate change".