DURBAN, South Africa - China's openness toward a legally binding climate deal that would come into effect after 2020 has given a boost to the ongoing climate change talks in Durban.

Experts said the flexibility that China showed is encouraging, but it's also important to pressure developed countries for much deeper emission reduction targets.

"China is willing to shoulder responsibilities in line with its development and capability as long as the legal framework after 2020 will comply with the principles of 'common but differentiated' responsibilities," Xie Zhenhua, China's top climate negotiator, said on the sidelines of the Durban meeting.

He laid out five preconditions of such a legal framework, including an extension of the Kyoto Protocol and actions by developed countries to help developing countries adapt to climate change.

Xie, deputy minister of the National Development and Reform Commission, said there are no new requirements, but countries need to implement the commitments and legal documents that have already been agreed to.

Tim Gore, Oxfam climate change policy adviser, said what seems to be missing in China's conditions is requesting deeper emission reduction targets from developed countries before 2020.

"This flexibility from China is really encouraging, which shows China is going to be a partner in building a regime we need to fight climate change. But we can't let the United States and other developed countries off the hook regarding emission reduction targets," he said.

"If we want to have a chance to make the global temperature rise stay under 2 degrees, we must have deeper emission reduction targets from developed countries before 2020, but not after 2020," he added.

The fate of the Kyoto Protocol, regarded as the cornerstone and most crucial issue at the meeting by developing countries, is still in the air one week into the conference.

Developed countries are being urged to sign onto a new round of enforceable pledges under the Kyoto Protocol, the only legally binding agreement that sets targets for major developed countries. The first commitment period of the treaty will expire in 2012.

So far, no country has said they will not continue the Kyoto Protocol, while some said they won't have a second commitment period after the first expires, Xie said.

"Hopefully these countries could find their appropriate positions," he said.

Canada, Russia and Japan said they will not agree to a second commitment period, while the European Union has showed a willingness to extend its commitments under the treaty but also suggested a broader global pact covering major emitters.

The length of a second commitment period will depend on what will be on the roadmap and what the timelines there will be, and what should be avoided is the gap between the two commitment periods, Connie Hedegaard, EU commissioner for climate action, told reporters on Monday.

If the new system comes into force earlier, Europe could have a short commitment period instead of a longer one, she said.

A plausible outcome of the Durban meeting seems to be that the EU and some other developed countries confirm their targets for a second commitment period, said Jonathan Grant, a senior sustainability and climate change manager of PricewaterhouseCoopers.

"But this is heavily caveated on actions by others. There is uncertainty around the legal form of these commitments, and the targets will be no more ambitious than those already declared," Grant said.

Xie also said previous agreements - including initiatives for technology transfer and new rules for verifying carbon cut promises - must be carried out.

China insists that a review of climate science should be finished by 2015, 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.

As a country with a per capita income of $4,300 and more than 120 million people living on less than a dollar a day, China will spare no efforts in countering climate change, Xie said.

China also announced it is looking to expand cooperation with climate vulnerable countries, such as small island states, least-developed countries and African nations, offering assistance for them to adapt to extreme weather events.

For instance, China will help build early warning systems for climate disasters and promote agriculture, forestry and water conservation technologies in those countries that are vulnerable to climate change.

Meanwhile, China will also assist in building hydro facilities and solar power projects to boost the use of renewable energy in the developing countries.

"China is also a victim of climate change. We share the same consequences brought up by global warming as these climate vulnerable countries. And we're actually standing together with them," Xie said.