Rich nations must agree to large, measurable cuts in their greenhouse gas emissions, if the world is to set a framework to tackle global warming at U.N.-led talks in December, a senior Chinese official said on Wednesday.

Xie Zhenhua, a deputy chief of the National Development and Reform Commission who steers climate change policy, told the official Xinhua agency that commitment from industrialized countries was crucial to a deal in Copenhagen in December.

The Chinese side believes that in Copenhagen...the key to success is to decide large, quantifiable mid-term emission-cutting targets for the developed nations, the Xinhua article paraphrased Xie saying.

He was speaking after the United States and China signed a deal that promises more cooperation on climate change, energy and the environment without setting firm goals.

Secretary of State Hillary Clinton said it highlighted the importance of climate change in U.S.-Chinese relations, and said the sides discussed in detail how to cut emissions ahead of the Copenhagen conference.

Xie's comments stopped short of Beijing's insistence earlier this year that developed nations should make cuts in greenhouse gas output of at least 40 percent below 1990 levels by 2020, suggesting the world's top emitter may be softening its stance with an eye on reaching a pragmatic deal.

Industrialized nations say that steep, expensive cuts in emissions are out of reach when they are trying to stimulate recession-hit economies.

And the key players who will be at the year-end talks have also been unable to reach consensus on other core issues like financing climate change adaptation programs in developing nations and the transfer of clean technology.

China is very vulnerable to a warming world. Its scientists have warned of more droughts in the north and extra storms and flooding in the south, as well as a potential drop in harvests of over one third by the end of the century.

Xie said last month, when the U.S. and Mexico were pushing ambitious long-term targets, that China preferred to focus on firm near-term cuts, which are harder to agree because they often require governments to make rapid and painful policy changes.

We support the existence of a long term target, so that the global community can have something to work hard toward, to motivate our efforts. But we think although long-term targets are important, mid-term targets are more realistic, he said then.

Only when we have a more positive, effective mid-term target can we judge whether or not we can achieve the long-term target.

China is the world's biggest annual emitter of greenhouse gasses but on a per capita basis and over the course of history it is far outpaced by western nations that have smaller populations and have had decades of emissions intensive growth.

It has long insisted that a framework to arrange and fund large-scale technology transfers should be a key part of any climate change deal, because it is the cheapest way to ensure the maximum possible cuts in carbon dioxide.

Officials also say it will help developing nations to curb emissions growth without having to sacrifice the development needed to lift their people out of poverty.

China Mexico Energy Hillary Clinton