China has abruptly slowed and halted work on building 22 major dams and power stations in a dramatic greening of the policies of the world's most populous nation.

The surprise move - one of the most dramatic ever undertaken by any government - arises from rapidly growing environmental concern in China. It calls the bluff of President George Bush, who has cited growing pollution in China as justification for refusing to join the Kyoto Protocol, which enters into force on Wednesday.

Last week Tony Blair went out of his way to welcome China's readiness to take "a real lead" in combating global warming. In the first instance of its kind, the Chinese State Environment Protection Agency laid down that the projects - which cover 13 of the country's provinces and are worth a total of £7.5bn - should not proceed until their impact on the environment had been reviewed. Among the halted projects is an important power facility at the highly controversial Three Gorges dam on the Yangtse River.

Observers attribute the move to growing interest in the environment by premier Wen Jiabao and other national leaders. Many of the children of top Chinese politicians and officials are members of the environmental pressure groups that are thriving at the country's top universities.

President Bush has cited the prospect of growing emissions of carbon dioxide from China as one of the main reasons for trying to kill the Kyoto treaty as "fatally flawed", and for his administration's attempts to try to stop the world agreeing to a successor.

But even before the latest move, China had already done far more than the US to combat the danger of climate change. Although its emissions of carbon dioxide, the main cause of global warming, rose rapidly between 1978 and 1996, they then fell sharply as a result of clean-up measures.

US government figures suggest emissions dropped by 17 per cent between 1996 and 2000, while the Chinese economy grew by 36 per cent. During the same period, US emissions grew by 5 per cent.