Japan's position is seen as crucial because it is trying to bring together the European Union, which supports the treaty on reducing greenhouses gases, and the US, which does not.

Koizumi is keeping quiet about Japan's position

Salvage

The talks in Bonn are the sixth round aimed at salvaging the 1997 Kyoto Protocol. The previous round, held in the Hague last November, collapsed in acrimony.

Issues to be discussed include the use of carbon 'sinks' like forests to soak up carbon emissions, funding for developing countries to improve their technology, and so-called "carbon trading", where developed countries pay for other countries' unused emissions rights instead of cutting their own.

Mr Koizumi's comments follow Japan's failure last week to persuade the US to return to the Protocol.

President Bush has said he will not sign a treaty which is not in his country's economic interests, but has so far failed to suggest an alternative.

Morocco talks

Mr Koizumi said the US would not reveal its thinking until the next UN climate conference in late October, to be held in Morocco.

He said Japan might also wait until then before unveiling its own position, presumably to maintain its bargaining strength.

"We have yet to reach a conclusion as we are trying to seek ways to cooperate between the United States, Europe and Japan. Under this stance, it will take until late October for our honest views to come out," he said.

Japan holds the key to the protocol's future.

In order to take effect, the Kyoto treaty needs to be ratified by countries accounting for at least 55% of the total 1990 carbon dioxide emissions from developed countries.

The EU and its allies, who have said they will ratify the treaty with or without US support, account for 49.5% of emssions. In order to pass the threshold they needs Japan's 8.5% of emissions.

The US accounts for 26%.