The tracks were laid along the Tanggula Mountain Pass, 255 meters higher than those that run along the Andes in Peru. Until Wednesday, the Peruvian railway that runs from the Pacific Coast up to the Andes at 4,817 meters was the highest railway point in the world for about 100 years.

The Qinghai-Tibet railway project is 1,142 kilometers long. It runs along the Qinghai-Tibet Plateau, also known by some as the "roof of the world".

Linking Gelmud in Qinghai with Lhasa in Tibet, the railway, when fully operational in 2007, will also boast the world's highest railway station at 5,068 meters above sea level and the world's highest transportation channel on ice at 4,905 meters. 960 kilometers of the railway will run 4,000 meters above sea level.

About 550 kilometers of the railway runs on ice or frozen earth, which "poses a major challenge to the railway construction," La Youyu, deputy director-general of the headquarters for the Qinghai-Tibet Railway construction, said.

"Frozen earth is vulnerable to climate change; it will thaw in summer, and contract and distend the railway base in winter, " La added.

The maximum train speed in the frozen earth areas is designed to reach 100 kilometers per hour and 120 kilometers per hour on non-frozen earth in actual operation, Vice-Minister Sun said, noting that it is "the most speedy for railways in frozen earth areas".

The gigantic Qinghai-Tibet Railway project was launched in June 2001, and so far 22.64 billion yuan (about US$2.8 billion) has been invested in the project.