Russia's parliament is due to vote on ratifying the Kyoto Protocol in the last hurdle before the long-delayed climate change treaty comes into force worldwide.
Russian ratification would push the 126-nation UN pact, aimed at battling global warming through curbing greenhouse gas emissions, over the threshold of 55 per cent of developed nations' emissions needed to make it internationally binding.
Friday's vote in the State Duma, controlled by pro-Kremlin parties, is the key to ratification, although if approved the bill still has to go through the upper house and be signed into law by its key advocate, President Vladimir Putin.
Moscow signed the 1997 Kyoto Protocol in 1999 but delayed ratifying it until May this year in exchange for EU agreement on the terms of Moscow's admission to the World Trade Organization.
Russia, which accounts for 17 per cent of world greenhouse gas emissions, became the key to Kyoto's future after the United States pulled out of the agreement in 2001.
Proponents of Kyoto say that apart from improving the environment worldwide, the pact would force Russia to upgrade its industry to new standards.
They also believe Russia, whose smokestack industries have cut emissions by about 30 per cent since the collapse of the Soviet Union, could earn billions of dollars by selling excess quotas for gas emissions to polluters abroad.
But opponents insist new emission limits could constrain Russia's economic growth and undermine Mr Putin's plan to double gross domestic product in 10 years.