The Kyoto protocol became fully operational on Wednesday after a UN climate conference here adopted the final rules setting out the functioning of the accord to limit pollution blamed for global warming.
Under the accord, 34 countries have agreed to limit emissions of so-called greenhouse gases up until 2012.
The protocol was negotiated in 1997 but could not come into operation until after the formal adoption of the Kyoto rulebook, which was drawn up over the past four years.
The final rules were adopted by consensus by the signatories to the UN framework convention on climate change at the conference. The United States and Australia have refused to ratify Kyoto.
The 12-day conference started Monday aiming to pass the final Kyoto measure and sketch plans for new pledges to cut greenhouse gases when the current commitment ends in 2012.