The meeting, attended by representatives from some 35 countries, was opened by Environment Minister Norbert Röttgen and South African Foreign Minister Maite Nkoana-Mashbane.
South Africa will host the annual meeting of the UN Framework Convention on Climate Change (UNFCCC) from November 28 to December 9 in Durban.
Chancellor Angela Merkel was due to address the gathering on Sunday afternoon.
In her weekly video podcast broadcast on Saturday, Merkel called for a binding agreement between industrialized economies on global warming to ensure that the world's temperature does not rise by more than two degrees Celsius.
“A number of countries announced (in the wake of the 2010 Cancun summit) voluntary measures, but these will not suffice to reach our objective," Merkel said.
"We also need measures, targeted measures, and if possible treaties that are legally binding. That's what will be difficult. But in any case, time is running short as the Kyoto Protocol is soon to expire," she added.
Kyoto is the only international agreement with binding targets for curbing
greenhouse gas emissions, but China and the United States, the world's biggest polluters, are not subject to its constraints. It expires in 2012, so there is pressure to make some progress at the summit later this year.
However, the European Union and the US have already indicated that no binding deal will be agreed in Durban.
Nevertheless, Röttgen said Sunday that it was a positive signal that China and the US had sent their chief climate negotiators to Berlin. “Everyone is here in whose hands it rests that progress is made,” he said. “No one has stayed away.”
South Africa's Nkoana-Mashabane emphasized that a similar meeting held last year in Germany, had been very helpful in preparing for the UN climate summit in Cancun, Mexico.
Greenpeace demonstrated outside the summit venue next to the Brandenburg Gate in central Berlin on Sunday, calling for rapid progress to prevent global warming. Activists climbed the facade of the building and unfurled a banner saying: “Take Leadership to save the Climate – Yes, you Can.”