Earlier this month, 171 governments put the final touches to the 1997 Kyoto Protocol on Climate Change, which binds industrialised countries to cut greenhouse gas emissions.

The latest negotiations, which follow four years of intense debate about how the protocol should be implemented, are likely to pave the way for when the treaty comes into force. This will establish a long-term basis for future international agreements on controlling emissions, as well as reducing emissions by 5 per cent from 1990 levels by 2008-12.

The agreement reflects a remarkable turnaround in the fortunes of the Kyoto Protocol. When US President George W. Bush declared his opposition to the Kyoto protocol on climate change earlier this year, it was widely assumed to mark the end of the accord.

But concern about the possible scale of climate change this century, coupled with a determination to preserve the multilateral negotiating process, persuaded governments to press on with the protocol without the US at Marrakech and at an earlier meeting in July in Bonn.

Now, governments will come under pressure swiftly to ratify the protocol, which requires the backing of at least 55 countries, representing 55 per cent of industrialised countries' 1990 emissions. That will require ratification by the EU, Russia, Japan and the rest of Europe which, together, produce 58 per cent of the industrialised world's emissions.

But in many countries, especially Japan, efforts to ratify the protocol are likely to meet with opposition from some sectors of industry, which are anxious about their potential loss of competitiveness if the US remains apart from the treaty.

Speculation about the future intentions of the US, which is the world's largest emitter of carbon dioxide, will continue to dominate debate about climate change. In the short term, there is little prospect of the US changing its mind on Kyoto. In a closing speech to the Morocco convention, Paula Dobriansky, the leader of the US delegation, said that the administration remained convinced that the protocol is "not sound policy".

The administration is still conducting a review of alternative climate change policies, although its attention has been focused elsewhere in the wake of September's terrorist attacks.

As yet, the events of September 11 have had little direct impact on the US climate policy, other than increasing concern about the security of future energy supplies from the middle east.

But the pressure from some US allies for it to reconsider its stance on the Kyoto Protocol is undiminished. Tony Blair, the UK prime minister, recently declared that "the power of the international community" gearing up to fight terrorism could be used to improve the environment. "We will implement it [Kyoto] and call upon all other nations to do so."

Despite the current unwillingness of the US administration to change course on Kyoto, many US commentators expect concessions on the environment in the run up to the Congressional elections next year. There is a growing expectation that Congress will introduce legislation introducing mandatory restrictions on the carbon dioxide emitted by the utilities, which account for about 40 per cent of US-wide carbon emissions.

Some commentators, such as Philip Clapp of the Washington-based National Environment Trust, believe this legislation could prompt a rethink on Kyoto. He reasons that the utilities would want to cut their compliance costs by buying emission "credits" created under the Kyoto emissions trading regime. That could lead to the US joining in negotiations, which are due to begin in 2005, for a future round of emission cuts, leading up to 2015.

But Frank Loy, under secretary of state for global affairs in President Clinton's administration, insists that the US would need to see some involvement by developing countries if it is to come back to the negotiating table. "The failure to address that issue is a political problem in the US. It is a legitimate issue. It has to be addressed."

Many climate experts agree that at least some developing countries must agree to limit the growth in their emissions, if the world's efforts to address climate change are to bear fruit. The Intergovernmental Panel on Climate Change, a group of UN-appointed experts, expects greenhouse gas emissions from developing countries to catch up with the industrialised countries between about 2015 and 2020.

However, winning the support of developing countries cannot be taken for granted. Under the 1992 UN Framework Convention on Climate Change, the developed countries agreed to take the lead in addressing climate change. Fierce debate is likely about whether wealthy countries have yet taken credible action on this score.

There will also be intense arguments about the basis on which developing countries can be drawn into the target-setting process. The approach used at the 1997 Kyoto conference was based on "grandfathering", by which countries' current emissions are the starting point for agreement on cuts. As more countries become involved in the process, the politics of such deals could become prohibitively complex.

Many politicians - and businesses making long-term investment plans - would prefer to agree on some overarching principles that would determine future emissions targets. For some policymakers, the answer is "contraction and convergence", an ambitious proposal for stabilising greenhouse gases under which every country would converge on the same emissions allocation per inhabitant by an agreed date.

This simple, bold approach has commanded support from many sources, ranging from President Chirac of France to the Chartered Insurance Institute of the UK. But wealthy countries may baulk at the stringency of the cuts it implies, which could be as much as 80 per cent by 2100.

Given the controversy surrounding the Kyoto Protocol, the international community has already achieved a stronger agreement than many sceptics thought possible. But as countries start to prepare the ground for the next stage of the global agreement on climate change, it is clear that past achievements are dwarfed by the magnitude of the challenges ahead.