The first week of negotiations of the UN Climate Conference in Durban was "progressive," said Christiana Figueres, UN top official on climate change.

Delegates will continue work this week to finalize a 130-page draft text, which will be the basis for a possible agreement, Figueres told a press briefing on Saturday.

Figueres, executive secretary of the UN Framework Convention of Climate Change (UNFCCC), said major parties have compromised on adaptation issues, such as how developing countries can tackle disasters and other impacts of climate change.

However, different parties are still wrangling over the key issues of the conference, namely the promises of developed countries to cut greenhouse emissions in the second commitment period of the Kyoto Protocol, whose first commitment period expires in 2012, as well as the Green Climate Fund.

The European Union ties its support for the Kyoto Protocol to a "roadmap" in Durban and a "mandate" in 2015 for a broader pact covering all major emitters, including the United States and emerging economies. It said the pact should take effect in 2020.

Meanwhile, U.S. negotiators have reiterated that they will not agree to any legally binding agreement, unless that agreement involves all major emitters.

Washington wants major emerging economies such as China and India to have legally binding commitments under the agreement.

Without new emission reduction pledges from wealthy nations, the Kyoto Protocol, an attachment to the UNFCCC and the world's only legally binding treaty by now, risks becoming an empty shell after its first commitment period expires in 2012.

Xie Zhenhua, head of the Chinese delegation, said Sunday that China agreed to discuss mandatory emission reduction targets after 2020.

But he called for a comprehensive and scientific appraisal of the first commitment period of the Kyoto Protocol before the formal negotiation of China's obligations after 2020.

Xie said China has strong political will to take responsibilities that match China's economic development and capabilities. He urged developed countries to bear their historical responsibilities for climate change and lead emission cuts.

Xie, terming China's position in the climate talks as "open, positive and constructive," urged other parties to further facilitate the negotiation process.

Analysts are hoping for breakthroughs this week when higher level officials with more political authorization take part in the negotiations.

"China has played a key role in climate talks," said Li Yan, an observer of the Durban conference. "In the first week it has showed strong desire to go forward."

"And next, we hope that China, the EU and other parties, can reach common ground on a fair, balanced and progressive outcome in Durban, overcoming the obstacles of the United States," said Li.