By Tristana Moore
BBC News, Berlin
Delegates to the United Nations Framework Convention on Climate Change and its Kyoto Protocol are meeting in the German city of Bonn.
The Kyoto Protocol binds 35 nations to cut carbon emissions
The two-week summit of about 2,000 delegates from 190 countries will focus on how to forward the Kyoto Protocol.
Kyoto binds 35 nations to cut carbon emissions in a first phase until 2012.
Officials will look at how to widen the deal to include the world's richest nations and the growing economies, such as the US, China, Brazil and India.
With Germany holding the presidency of the G8, Chancellor Angela Merkel has pledged to put climate change at the top of the agenda when leaders of the world's richest nations gather at the G8 Summit in Heiligendamm next month.
Experts meeting in Bonn are set to outline guidelines for limiting national greenhouse gas emissions, and reducing emissions from deforestation in developing countries.
The main focus will be on what happens when the current phase of the Kyoto Protocol, which sets out legally binding emission targets, ends in 2012.
China had argued against anything which could affect its growth
European nations hope the US and Australia, which have not ratified the Kyoto Protocol, will agree to cut their emissions of greenhouse gases under a new deal.
UN officials say the challenge is to come up with an international agreement which brings together the world's richest nations and the growing economies of China, India, Brazil and Mexico.
During two weeks of talks, there will also be workshops on energy efficiency, greater use of renewable energy and technologies to develop clean fossil fuels.
The discussions are aimed at paving the way for December's meeting of environment ministers in Bali, where it is hoped delegates will reach consensus on a follow-up to Kyoto.