The Russian government has approved the Kyoto Protocol on climate change and sent it to parliament for ratification.
Until now, Moscow has wavered over the treaty, which can only come into force with Russian ratification.
The Kyoto Protocol sets targets for greenhouse gas emissions, which many scientists believe cause global warming and climate change.
President Vladimir Putin earlier made his support for Kyoto known, but divisions emerged among his aides.
Mr Putin's chief economic adviser, Andrei Illarionov, said the treaty would stifle economic growth.
The necessary law on ratification is set to pass through the Russian parliament unhindered and, in theory, the treaty could come into force within three months.
The lower house, the State Duma, is dominated by the pro-Putin United Russia party.
Bryony Worthington of environmental campaign group Friends of the Earth expressed delight at the Russian decision.
"We are very pleased, this is a hugely significant development politically and it will increase pressure on countries like the US and Australia, who have so far remained outside the only international agreement to curb greenhouse gas emissions," she told the BBC.
"It has to be recognised that Kyoto is only the first step and discussions must begin immediately on what happens after Kyoto," she added.
Since the US, the world's biggest polluter, pulled out three years ago, the treaty has been dependent on Russian ratification. Russia accounts for 17% of world emissions.
Political gains
Interfax news agency said that, according to the government decision, ministries linked to the environment had been given three months to work out a series of practical measures arising from Russia's obligations.
President Putin ended the confusion over Russia's stance in May, when he spoke of his desire to see the treaty ratified.
But some top Kremlin economists have questioned how Russia could reduce greenhouse gas emissions when it is enjoying an industrial revival and has set itself the target of doubling GDP within a decade.
This week top Russian scientists advised against ratification, claiming there was no evidence linking greenhouse gas emissions to climate change.
But the deciding factor appears to be not the economic cost, but the political benefits for Russia.
In particular, there has been talk of stronger European Union support for Russia's bid to join the World Trade Organization, in response to its ratification of the treaty.
