As government ministers gather in The Hague for the UN conference on climate change, the president of the talks, the Dutch environment minister, Jan Pronk, has warned there is no guarantee of success for international efforts to halt global warming.
He said everything now depended on the delegates' willingness to compromise.
The Kyoto Protocol, agreed in Japan three years ago, commits nearly 40 developed countries to cut their emissions of carbon dioxide and five other greenhouse gases, which many scientists are convinced are responsible for global warming.
Emissions
The overall cuts would reduce emissions of the gases by 5.2%, compared with their 1990 levels, by some time between 2008 and 2012.
One of the stumbling blocks at the talks, which began a week ago, has been the insistence of the US and a number of other developed countries that they should be allowed to achieve much of their Kyoto reduction targets without actually reducing their emissions at all.
The protocol offers ways for them to do this, for example, by buying emission rights from countries which cannot use them, or by funding clean energy schemes in developing countries.
Compromise
Speaking to journalists after an informal meeting of 35 countries, Mr Pronk said: "The list of what has been achieved so far is not long. The task ahead of us is much bigger, and very difficult. I am frustrated with the pace of the talks over the last three years.
"The pace this last week was a bit quicker. But if we go on at this same pace, we will still be talking in 2008. We need the politicians' involvement to move things on."
The conference moves onto a higher plane on Monday, with the arrival of government ministers from many countries to take over the preparatory work done by their officials.
Mr Pronk said compromise was now the key.
"I see movement in the right direction from the two extremes," he said.
"If that movement can be speeded up by the politicians, we'll be going in the right direction. There is a real chance. But the chance is not big."
Forests
The US denies strenuously that it is seeking to hold up any deal, and says it remains totally committed to tackling climate change.
Worryingly, though, US sources are saying that they have already offered compromises, and that they believe no-one else has yet done so.
They say they have shown their good faith by agreeing not to argue for nuclear power as a major way of offsetting greenhouse emissions.
And they say they have shown their willingness for a gradual phase-in of the use of forests, which absorb carbon dioxide while the trees are growing, as a legitimate way of reducing emissions.
The prospects for the sorts of compromise Mr Pronk is searching for before the conference ends on 24 November seem slim.