Chinese engineering company completed on Sunday the first over-1000-meter tunnel along the China-Laos railway.

Nateuy No. 1 Tunnel, some 360 km north of Lao capital Vientiane, is located in the northern Lao province of Luang Namtha bordering China in the north.

Huang Zongwen, a senior official with the China Railway No. 5 Engineering Group (CREC 5), which is in charge of the tunnel's construction, told Xinhua the construction of the Nateuy No. 1 Tunnel, with 1158 meters, was started on June 3, 2017.

"That the tunnel passes soft rocks all the way in the mountain, brought some difficulties in construction and especially, affected the digging pace," Huang said.

In December 2017, Ban Somsanook No. 2 Tunnel with a length of 301 meters in Laos' Vientiane Province, was bored by the Chinese project contractor Sino Corporation Engineering Bureau 15 Co., Ltd., and became the first completed tunnel along the China-Laos railway route, and the first road and railway tunnel in Lao history.

The China-Laos railway is being promoted by the leaders of the two countries as a project of interconnectivity. Since the commencement of construction in December 2016, the building of tunnels, bridges, roadbeds and other sections has progressed smoothly.

The China-Laos railway has a total length of more than 414 km comprising 60 percent of bridges and tunnels (around 198 km), linking Mohan-Boten border gate in northern Laos and the capital of Vientiane.

The operating speed of trains on the route is designed to be 160 km per hour. The railway is expected to be fully operational in December 2021.