He said: "Without China, there can be no success this year on a new global climate framework."
China has already become a world leader in wind and solar technology, he said. The renewable energy sector is worth $17b and employs nearly one million people in China, according to the UN.
The secretary general said China could "blaze a new trail for the world" and "create a new clean-energy path to prosperity".
China is the world's leading emitter of carbon dioxide, according to Yang Fuqiang, a climate change expert at WWF International.
"If it's just business as usual, China will account for 25% or more of the world's carbon dioxide emissions by 2030," said the Beijing-based expert.
Carbon dioxide is emitted by burning fossil fuels such as coal, oil and gas and is a key driver of global warming.
But Mr Yang said China was already trying to reduce its carbon dioxide emissions by developing renewable energy sources.
It is also improving energy efficiency, developing nuclear power and working on schemes that capture and store pollutants.
China hopes to provide 15% of its energy consumption from renewable sources by 2020, added Mr Yang.
Senior US officials have recently visited China to discus the meeting in Copenhagen later this year. They said they were optimistic about what they had heard.