China's high-speed, high-altitude railway to Tibet has carried troops to the regional capital, Lhasa, for the first time, state media has reported.
The railway snakes for 1,140km across 'the roof of the world'
The Xinhua news agency cited unnamed sources in the People's Liberation Army as saying the railway would become "a main option" for transporting soldiers.
Analysts say the move is likely to fuel concerns that China is using the rail link to tighten its hold on Tibet.
Chinese tourism and trade to Tibet has surged since its opening 17 months ago.
Journey times cut
The $4.2bn (£2.1bn) Qinghai-Tibet line boasts high-tech engineering to stabilise tracks over permafrost and sealed cabins to protect passengers from the high altitude.
China says the 1,140km (710-mile) line has cut travel time to Lhasa from Beijing and other cities to just two days.
Previously, Lhasa could be reached only by plane or after a long, arduous road journey.
Trains now carry about 75% of all goods between Tibet and other parts of China, according to Xinhua.
Tourism also soared by 64% during the first 10 months of the year, to 3.72 million tourists, compared with 2006, a separate report said.
Critics say the railway line threatens not only the delicate Himalayan environment, but also the ancient Tibetan culture.