China's top climate negotiator Xie Zhenhua on Sunday laid out conditions under which Beijing would accept a legally-binding climate deal that would go into force after 2020, when current voluntary pledges run out.

The conditions included a renewal of carbon-cutting pledges by rich nations under the Kyoto Protocol, along with hundreds of billions of dollars in short- and long-term climate financing for poorer countries.

"I think after 2020 we should also negotiate a legally-binding document," Xie told a group of NGOs at talks in Durban under the UN Framework Convention on Climate Change (UNFCCC).

"The problem now is that we have to see whether we have conscientiously implemented the legal documents we already have agreement on. This is a very important issue for us," he said through an official Chinese translator.

The 194-nation talks, which wrap up Friday, are abuzz with speculation on the prospect of a "Durban accord".

Such a deal could set a pathway for a binding climate pact that would include not just rich countries, as does the Kyoto Protocol, but all major greenhouse emitters, including China, India and Brazil.

Major emerging economies and other developing nations already emit more than half of current carbon emissions, and within 20 years are projected to account for two-thirds.

The European Union launched the idea, tying its support of the Protocol -- which risks becoming an empty shell in 2012 without new carbon cutting pledges from industrialised nations -- to a "mandate" for a broader 2015 climate pact.

The United States has reacted coolly to the proposal, as has India while host country South Africa, and perhaps Brazil, have expressed a greater openness.

A senior US official, speaking on condition of anonymity, said he had not spoken to Xie or seen a copy of the Chinese minister's comments.

"The question is, what are they prepared to agree to here in Durban," the official said.

The first of some 130 ministers expected for a high-level session beginning Tuesday arrived over the weekend.

After first saying the EU bid was "too much," China has in the last few days hinted that it might be willing to take on legal obligations under an new international framework.

Until now, it has insisted that as a "developing" country it was exempt from such obligations.

While Xie said China has 122 million people living on less than a dollar a day, Beijing would continue to boost its climate-fighting efforts in step with its development.

Xie enumerated five conditions for China taking on pledges under a new accord that would go into effect after 2020, in response to a question from Alden Meyer, a policy analyst from the Union of Concerned Scientists.

One is that the European Union and "other countries" sign on to a new round of enforceable pledges under Kyoto.

Europe has signalled its willingness to extend its commitments by five, perhaps eight years, but the chances that it would do so under the treaty's laborious ratification process seem remote.

So-called "fast start" climate financing for poorer countries of $30 billion for the period of 2010 to 2012 must also be delivered, Xie said. Likewise a Green Climate Fund that would ramp up to $100 billion per year by 2020.

A raft of nut-and-bolts agreements outlined at the 2009 Copenhagen summit and married into the UN process at last year's high-level climate gathering in Cancun, Mexico must also move forward.

These include initiatives for technology transfer, adaptation -- helping vulnerable nations cope with impacts -- and new rules for verifying that carbon-cutting promises are kept.

Finally, China insists that a review of climate science begin as planned in 2013, and that established principles in which historical responsibility for creating the problem of climate change, and the respective capacity of countries to fight it, are respected.