The WWF conservation group said the 1997 pact, which is dependent on Russia's final approval if it is to come into force despite a U.S. pullout in 2001, could be ratified by the Russian parliament within the next few weeks.
Russian officials were not immediately available to comment.
"Putin has instructed key ministers to sign the Kyoto ratification documents," WWF said in a statement, saying he had met key advisers on Kyoto last week. Once ministers had signed, the documents could go to parliament for formal ratification.
But Russian ratification has often slipped before amid divisions among officials - Putin said in May that he would speed up the ratification process after months of indecision.
"I'll believe Russia has signed up to Kyoto once it's done but this is the most positive step we've had in a very long time," said Steve Sawyer, climate policy director at environmental group Greenpeace.
"This is a significant step toward Russian ratification," said Jennifer Morgan, director of the WWF's climate change program. Environmentalists have sometimes in the past gained access to unpublished Russian government documents on Kyoto.
Kyoto is a first step toward curbing emissions of gases like carbon dioxide, largely released from burning fossil fuels in power stations, cars, factories and homes.
U.N. scientists say carbon dioxide is building up in the atmosphere and trapping the sun's heat. The resulting global warming may lead to disastrous heatwaves, floods, hurricanes and raise global sea levels.
Documents obtained by Reuters in Moscow earlier this month showed that Prime Minister Mikhail Fradkov and some key ministries doubted Kyoto's scientific basis.
Kyoto hinges on Moscow to come into force because it needs to be ratified by countries representing 55 percent of carbon dioxide emissions by developed nations. It has reached about 44 percent and cannot reach the threshold without Russia's 17 percent after the United States, the biggest polluter with 36 percent, pulled out.
President Bush said that Kyoto was too costly and unfairly excluded developing nations from goals for a first period, until 2012.
Backers of Kyoto, including European Union states, have said they will go ahead and cut carbon dioxide emissions whatever Russia decides.
But Energy Commissioner Loyola de Palacio told EU lawmakers Tuesday that the EU should reconsider its plans for emissions trading if Russia fails to ratify by December.
In January 2005, the EU will launch a scheme allowing industrial companies to buy or sell rights to pollute to meet the bloc's commitment under Kyoto.