US Sen. John Kerry recalls meeting the Chinese in the early days of negotiations in the 1990s on a treaty to control greenhouse gases emissions blamed for climate change. "Usually, we just stared at each other," said the Massachusetts Democrat.

"They just wouldn't hear of anything. They saw this effort as a Western conspiracy to prevent them from growing," Kerry said in a conference call with reporters last week.

That changed a year ago when China agreed developing countries would help contain carbon emissions, as long as the wealthy industrial countries gave them the needed technology and finances.

"Now there is a transformation in China that opens up possibilities," said Kerry, who is in line to become chairman of the powerful Senate Foreign Relations Committee which closely monitors international climate issues.

China has a long way to go. It depends on carbon-laden coal for 70 percent of its power, and has plans to build more than 550 coal-fired power stations. Its capital is so polluted that it had to close much of its industry and order cars off roads last summer so athletes could compete in the Beijing Olympics.

Last year, China overtook the United States as the world's largest emitter of greenhouse gases, according to the Netherlands Environmental Assessment Agency, and accounted for two-thirds of the global increase in carbon emissions in 2007.

Yet the Chinese still emit about one-fourth as much carbon per person as the average American.

China insists it won't sacrifice development to convert speedily to a low-carbon economy.

"In this world, there are still some people who are living in abject poverty. For them, subsistence comes first," said Chinese Foreign Minister Yang Jiechi, speaking Tuesday in Hong Kong.

But the Chinese compromise last year broke a long-standing deadlock between industrial and developing countries on sharing a burden that has been shouldered until now only by industrial nations.

"That was a very big step," said Li Yan, of the environmental group, Greenpeace. "Now the challenge is not to say what is the next step, but to implement" policy with Western financial help.

Delegates beginning another two-week session in this medieval Polish city say China's more open policy is critical to an agreement on a treaty that will replace the Kyoto Protocol, the 1997 accord, which requires 37 countries to reduce greenhouse gases by an average 5 percent by 2012.

That accord was rejected by the United States because China, India, Brazil and other big-polluting economies were exempt from any obligations to curb their own emissions.

"If we are to achieve a comprehensive climate deal we need a very strong Chinese engagement," Denmark's Prime Minister Anders Fogh Rasmussen said Monday. "I am pleased to note a strong Chinese commitment to mitigating climate change," said the Danish leader, who visited Beijing last month. The new treaty is due to be completed next December in the Danish capital, Copenhagen.

While more flexible than in the past, the Chinese still balk at accepting specific targets, like industrial countries. They also want the rich countries to commit to donating 1 percent of their gross domestic product to help poor countries fight global warming.

Jake Schmidt, of the Washington-based Natural Resources Defense Council who visits Beijing regularly, says the Chinese have been saying privately for a long time what they refused to say publicly.

"When you came to these formal negotiations they took a different tone," Schmidt said in an interview. "They're tough negotiators. They're good."

Last month China issued a revealing "white paper" that laid out its policies and the reasons behind them.

It said China has had 21 warm winters since 1986, the flow of water in its northern rivers has slowed while its southern rivers have experienced more floods. Its glaciers are melting, threatening future run-off and water reserves. The sea level is rising along its 11,200-mile (18,000-kilometer) coast, damaging wetlands, coral reefs and marine life.

China is ready to do its share on climate change, the document said, while working to ease poverty among its 1.3 billion people.

"Climate change arises out of development, and should thus be solved along with development," it said.

"Both developed and developing countries are obligated to adopt measures to decelerate and adapt to climate change," it added, but insisted industrial countries have a historic responsibility to lead the way.

About 70 percent of China's carbon emissions are produced by heavy industry, compared with 20 percent in the United States where the bulk of emissions comes from cars, home heating and service industries.

Yet the Chinese have adopted progressive measures to control pollution.

Their vehicle emissions standards are among the world's most stringent, and they have resolved to use less power to produce goods. Last year alone, the white paper said, China used 3.7 percent less energy to produce one unit of gross domestic product.

In each of the last two years China has more than doubled its renewable energy

capacity, and is now the world's fifth largest user of wind turbines, said Li, the Greenpeace activist.

"Green energy is booming," she said, but added China still must move away from coal faster. "Even at such unprecedented growth, considering the challenge of climate change, a lot needs to be done on a far larger scale."

China has closed 11,200 small coal mines and 2,000 inefficient and heavily polluting paper and dyeing mills and chemical plants.

Schmidt, the environmental analyst, said he expected China's policy to continue evolving.

"One of the stumbling blocks was the lack of U.S. leadership." With the climate-friendly policies of President-elect Barack Obama, "you'll notice the change in the rhetoric and tone will continue," he said.

"They'll still be hard negotiators."