TROMSOE, Norway - The United Nations welcomed China's pledge to do more to tackle climate change and called on the world's richest nations to help poorer developing states invest in technology needed to reduce carbon emissions.

"I welcome this step very much ... We cannot ask for more at this stage," Achim Steiner, head of the U.N. Environment Programme, told reporters on the sidelines of a climate change conference in northern Norway.

China unveiled a climate change plan on Monday but said it would not sacrifice economic ambitions to international demands to curb emissions blamed for global warming.

Steiner said developing countries like China should focus on greener technology, such as building natural gas-fired power plants instead of coal-burning facilities.

"The infrastructure now being built will serve for the next 30-50 years and the technology choices and standards applied will lock China, or South Africa for example, into a certain level of emissions for decades," he said.

"That is why we need ... industrial nations to help developing states chose tomorrow's technology, not yesterday's."

He said developed industrial countries, where emission regulations were often more restrictive, would gain more by striving for a greater share of renewable energy and more energy efficiency.