The Chinese President, Hu Jintao has announced his intention to achieve a significant reduction in the growth of his country's C02 emissions over the next decade.
Speaking at the United Nations in New York, he said China would endeavour to curb its carbon emissions per unit of Gross Domestic Product by a "notable margin" by 2020 from the 2005 level.
The move has prompted hopes that a global climate deal could be reached at the Copenhagen climate conference in December.
Yvo de Boer is executive secretary of the United Nations Framework Convention on Climate Change.
It is his job to drive the process forward, look for solutions and it is hoped, clinch that elusive deal at the end of the year.
Mr De Boer says he was encouraged by the Chinese move.
Until now, Washington has been accused of using China's refusal to set targets as an excuse for dragging its own feet over action on climate change.
So, what impact will President Hu's speech have on the US government?
Henry Lee is an expert on China's energy strategies at Harvard University.