The treaty's supporters had hoped that President Vladimir Putin, who offered to organise the conference at the 2001 Group of Eight conference in Genoa, Italy, would use the meeting to announce that Russia would ratify the protocol, thereby bringing it into force.

But on Thursday Deputy Prime Minister Alexei Gordeyev told reporters that Russia has "no schedule" for ratifying the treaty.

It was not clear Friday whether Putin, who is due to meet with US President George W. Bush in the United States at the weekend, would return in time to open the conference.

Gordeyev had earlier said that Putin would open the conference.

Around 500 scientific papers are due to be presented to the conference which will convene some 1,200 experts from 43 countries.

Kyoto is not officially on the agenda for debate but it will be on every delegate's mind and Russia's apparent ambivalence towards the treaty has left its Western partners baffled.

The pact provides for a worldwide reduction in the emission of greenhouse gases held responsible for global warming, notably carbon dioxide.

But to come into force it requires the ratification of countries representing at least 55 percent of the total of carbon dioxide emissions worldwide.

The United States has refused to ratify the treaty and Russia's signature is needed to pass the threshold.

Only three Western countries -- Canada, France and Italy -- are sending their environment ministers to the Moscow conference.

Others such as Britain and Germany, along with the European Commissioner for the Environment Margot Wallstroem, made it clear they would not sanction by their official presence an event whose political outcome was uncertain.

"We have always said that our participation would depend on receiving a clear gesture from Moscow in favour of the protocol which does not appear to be forthcoming," officials close to Wallstroem said.

Among the major developing countries, China and India are sending a minister or a deputy minister.

The United States is to be represented "on an individual basis" by a scientific official, Conrad Lautenbacher, undersecretary for trade, and by its main negotiator on climate affairs, Harlan Watson.

The Kyoto treaty, signed in 1997, has been ratified by 117 countries but these account for just 44.2 percent of global carbon dioxide emissions.

Ratification by Moscow, which accounts for 17.4 percent of CO2 emissions, is needed to bring the total past the 55 percent mark.

In September 2002 both Putin and Prime Minister Mikhail Kasyanov hinted strongly at a Johannesburg summit that Russia would eventually ratify the pact.

But since then, Russian officials have issued a series of contradictory statements on the matter.

The most recent damper came on July 21 when Putin, writing to European Union leaders, argued for "mutually acceptable outcomes" to disputed issues, among which he included trade, energy and the environment, implicitly linking a Kyoto ratification to Russia's application to join the World Trade Organisation.

Canadian Energy Minister David Anderson told AFP in a telephone conversation that when all is said and done, Russia will probably ratify Kyoto "but in their own way, in their own time."

SPACE.WIRE