XI'AN -- Construction work started Saturday on a major high-speed railway in China's western hinterland to promote local economic cooperation and development.

The 643-km-long railway line for passenger transport links Xi'an, capital of Northwest China's Shaanxi province to Chengdu, capital of the southwestern province of Sichuan.

The project will be completed in five years with an investment of more than 40 billion yuan ($6.35 billion). The travel time between the two cities will be shortened to three hours from 12 hours currently, after the new railway is put into operation.

The line will have 127 km of tunnels to pass through the Qinling Mountains.

China aims to basically complete the construction of a high-speed railway network with a total operating length of more than 40,000 km by the end of 2015.