The United Nations said yesterday that rich countries' failure to honor their commitments to transfer resources and technology remains "the single biggest obstacle" to address the global climate change challenge.

Nearly two-thirds of the key technologies that China needs to mitigate global warming should be imported from the developed economies, said an expert of the country's climate change negotiation panel.

Zou Ji, environment policy professor with Beijing-based Renmin University of China, said China badly needs 62 key technologies in nuclear electricity, bio-fuel, carbon capture, wind power turbines and smart grid to realize its goal of energy efficiency and sustainable development in key industrial sectors.