Russia is expected to announce targets of cutting its carbon emissions to between 15 and 25 percent below 1990 levels when chief negotiator Alexander Bedritsky addresses the forum in Doha, Qatar, on Thursday.
That target, included in a draft presidential decree written by the Natural Resources and Environment Ministry, retreats from a commitment in June by Prime Minister Dmitry Medvdev at the UN Sustainable Development Conference in Rio de Janeiro to slash emissions by 25 percent.
Bedritsky said Wednesday that Medvedev's prior statement would still "guide" Russian policy.
"I would recommend focusing on Prime Minister Medvedev's statement in Rio," he told journalists, RIA-Novosti reported.
Environmentalists say Medvedev's target already lacks ambition because emissions nose-dived with the collapse of industry following the breakup of the Soviet Union and have still not recovered.
According to the Federal Service for Hydrometeorology, Russia emitted 2.16 billion tons of CO2-equivalent in 2009, 35.6 percent lower than 1990 levels.
Environmentalists say that if the role of Russia's vast forests as a carbon sink is taken into account, emissions are even lower, meaning the target set by the government is in reality a license to increase emissions.
Russia has joined Canada and Japan in refusing to sign up for a second implementation period of the Kyoto Protocol.
The Russian government has so far ignored growing domestic pressure from environmentalists, economists and businessmen to embrace Kyoto 2.
UN Secretary-General Ban Ki-moon on Wednesday blamed rich countries for global warming and said the developed world should take the lead in reducing emissions.
"The climate change phenomenon has been caused by the industrialization of the developed world," he said on the sidelines of the conference. "It is only fair and reasonable that the developed world should bear most of the responsibility."