Russian President Vladimir Putin is facing criticism from around the world for refusing to set a timetable for ratifying the Kyoto climate change agreement.
Much of Russia's industry has been lost since communism collapsed
At the opening of a major conference on global warming in Moscow, Mr Putin said his government was still studying the pros and cons of ratification.
Russia's approval is vital for the 1997 pact to acquire the force of international law, after the United States pulled out two years ago.
Mr Putin had been urged to use the conference to confirm Russia's ratification and his comments have drawn protests from the United Nations, European Union and environmentalists.
Norway's Environment Minister Boerge Brende said Mr Putin had promised a year ago that Russia would ratify the treaty "soon".
"Without Russia, and when the US and Australia is not on board, there will be no Kyoto Protocol. And climate change is taking place," he said.
US denies pressure
To come into effect, the protocol requires the ratification of countries representing at least 55% of the global total of carbon dioxide emissions.
With the US refusing to take part, all the other major industrial powers must ratify the agreement for the quota to be reached.
Meanwhile, BBC environment correspondent Tim Hirsch says a senior American official has strongly denied putting pressure on Russia to stay out of the Kyoto agreement.
Some European government figures claim privately that the US has been working behind the scenes to encourage Russia to sabotage the treaty.
But the American chief climate negotiator Harlan Watson told the BBC he categorically denied that.
He said President Bush had pledged not to influence other countries one way or another on whether to go ahead with Kyoto.
'There will be floods'
The environmentalist group Greenpeace warned that "[Mr Putin's] stalling could now derail the entire process".
UN Secretary General Kofi Annan urged Russia to immediately approve the agreement.
Climate change means wetter winters and drier summers for some
"I join people throughout the world in eagerly awaiting ratification by the Russian Federation, which will bring the protocol into force and further galvanise global action," he said, in a message to the conference.
The EU, which plans to limit emissions from its own industries from 2005, also reiterated its call for Russia to sign up.
But Mr Putin was ambiguous about his views on Kyoto.
"[Critics of the pact] often say, half-jokingly and half-seriously, that Russia is a northern country and if temperatures get warmer by two or three degrees Celsius it's not that bad - we could spend less on warm coats and agricultural experts say that grain harvests would increase further," he told the conference.
"That may be so, but... we must also think what consequences we will face in certain regions where there will be droughts and where there will be floods."
Our correspondent says international observers are puzzled as to why Russia has such a problem with Kyoto since, on the face of it, the country has secured an extraordinarily good deal from the agreement.
Its target for the period 2008-12 is to keep emissions of carbon dioxide and other gases linked to climate change at the same level as in 1990, compared with an average cut of just over 5% for the industrialised world as a whole.
But since 1990 coincided with the collapse of traditional state-subsidised industry after the demise of the Soviet Union, emissions are already much lower than they were - not because factories are a lot cleaner, but simply because there are fewer of them.
Under the Kyoto system, this leaves Russia with "spare" pollution allowances which it can sell to other countries to help them fulfil their own targets.