Construction of a tunnel that will traverse Trola Mountain in southwestern Sichuan Province began on Wednesday.
At an altitude of 4,240 to 4,380 meters, the Trola Mountain tunnel will be the world's highest.
The tunnel is on the Sichuan-Tibet Highway that links Chengdu, Sichuan in the east with Lhasa, Tibet in the west.
The 7-kilometer tunnel will shorten travel time across the mountain from more than two hours to only about 10 minutes, construction manager Li Ming said.
Workers must first build an approach that is 14.06 kilometers long on the east side of the mountain, Li said.
The tunnel is scheduled to be completed in four years with an investment of 1.12 billion yuan (172 million U.S. dollars).
The 2,415-kilometer Sichuan-Tibet highway is considered one the world's most deadly as it traverses a dozen rivers and 14 mountains with altitudes of 4,000 to 5,000 meters.
