The law on ratification, passed last week by the lower and more powerful chamber, the State Duma, was approved by 139 of the chamber's 178 senators, well above the 91 votes for the required two-thirds majority.

Following his signature, which is regarded as only a formality, Putin will transmit Russia's ratification of the treaty to the United Nations.

The historic vote last Friday in the Duma virtually guaranteed that the UN global warming pact would come into force, despite a decision by US President George W. Bush to walk away from the agreement.