Outlining a second commitment period for the Kyoto Protocol is the chief priority of the United Nations climate change talks in Durban, China's chief climate negotiator said Tuesday.

Speaking on behalf of Brazil, South Africa, India and China, which agreed to form a negotiating bloc at the Copenhagen climate summit in 2009, Su Wei encouraged policymakers to recommit to the protocol, calling it a cornerstone of the global climate regime and an essential foundation of a rules-based system.

The Kyoto Protocol was passed in December 1997 and came into effect in February 2005. It sets binding targets for developed countries on the reduction of greenhouse gas emissions.

Unless actions are taken to extent Kyoto, its mandate will expire at the end of 2012. Developing countries support the definition of a second commitment period, while a number of developed countries oppose it. In the lead-up to the conference, Japan, Russia and Canada said they would not sign on to a second commitment period.

"Sustainable development and poverty eradication remain urgent challenges and overriding priorities for our countries. But our countries have pledged ambitious actions to reduce emissions at substantial cost to their economies," Su said.

Brazil, South Africa, India and China expect developed countries to "rise up to their historical responsibilities" and take the lead by undertaking "ambitious and robust mitigation commitments consistent with science," Su said.

Su also addressed financing, another hot issue at the climate change negotiations, calling for the immediate operationalization of the Green Climate Fund, including funding by developed countries and accountability to the Conference of the Parties.

Su said the four-country bloc recognizes adaptation as the most urgent task for developing countries, and supports African nations' position on prioritizing this issue at Durban.

The bloc calls for immediate operationalization of the Adaptation Committee, which should contribute to adaptation policy development and implementation of adaptation actions in developing countries following the requests of developing countries and respecting a country-driven approach.

"We believe that the Durban Conference should achieve a comprehensive, fair and balanced outcome to enable the full, effective and sustained implementation of the Convention and its Kyoto Protocol, in accordance with the principles of equity and common but differentiated responsibilities and respective capabilities, and fulfilling the mandate of Bali Roadmap in the two-track process of negotiation," Su said.

China reaffirmed continued full support for South Africa to make Durban Conference a success in an open, transparent, inclusive and party-driven process, Su said.

The 12-day talks are the 17th session of the Conference of the Parties to the United Nations Framework Convention on Climate Change. Opened on Nov. 28, the 12-day conference has attracted 30,000 participants from more than 190 countries.