China's controversial railway to the remote and restless mountainous region of Tibet could be threatened by global warming, which may melt the permafrost on which the tracks are built, state media said on Wednesday.

'In Tibet, the mercury has climbed an average of 0.32 degrees Celsius every decade since records began in 1961,' China Meteorological Administration head Zheng Guoguang was quoted as saying by the official Xinhua news agency.

'This is much higher than the national average temperature rise of 0.05-0.08 degrees Celsius every 10 years,' Zheng added, speaking at a meeting in the Tibetan regional capital of Lhasa.

Tibet, being so high, acted as a 'magnifier' for global warming, Zheng said.

'The impact of global warming has accelerated glacial shrinkage and the melting glaciers have swollen Tibet's lakes,' Zheng added. 'If the warming continues, millions of people in western China would face floods in the short term and drought in the long run.

'In the worst case, such warming could cause permafrost to melt and threaten the plateau railway linking Tibet with (neighbouring) Qinghai province,' the report paraphrased him as saying.

Beijing has said it wants to combat climate change yet ensure China's economic development is unimpeded. Xinhua said the government believes the railway will be safe to use for the next 40 years if the thaw continues at its present speed.

Over the last two decades it has spent more than 1 billion yuan ($146.6 million) reinforcing the main highway to Tibet, where the permafrost is also melting, Xinhua added.

China says the 30 billion yuan rail line, opened in 2006 and passing through towering mountains and vast deserts, will help bring economic development to ethnically distinct Tibet.

Tibetan activists, however, say it speeds the immigration of Han Chinese to Lhasa and the plateau, and allows increased exploitation of Tibet's significant mineral resources.-Reuters