China's governor in Tibet says a railway system linking the region to the rest of China is being extended from Lhasa, the capital, to Tibet's second-largest city, Shigatse.
The rail link to Tibet is not yet fully operational, but Xinhua news agency reports plans are already in motion to extend the line across rugged terrain west of Lhasa to Shigatse.
Tibet's regional administrator Jampa Phuntsok is quoted as saying the new project should be completed within five years.
China's railway into Tibet is the world's highest. Eighty percent of the line is above four thousand meters in altitude, and it rises above five thousand meters in some places -- high enough that passenger coaches must be pressurized in the same way as aircraft cabins.
Shigatse, on the Zango (Brahmaputra) River about 225 kilometers west of Lhasa, is known for its ancient monasteries and temples. The city is the traditional home of the Panchen Lama, the second most important figure in Tibetan Buddhism after the Dalai Lama.
Critics say the railway will harm Tibet's environment by opening its timber and mineral resources to further exploitation. They also warn that Tibet's Buddhist culture could be diluted by a flood of migrants from China.
Chinese officials say the railway will open new markets for Tibetan products and boost its tourism industry.
Originating in the western Chinese city of Golmud, the high-altitude line to Lhasa stretches almost two thousand kilometers and cost more than three billion dollars. Xinhua reports construction was completed in October, and trial runs are set to begin in July.