The cross-border tunnel on the China-Laos Railway was completed on Sunday, according to local authorities.

The "friendship tunnel," with a total length of 9.59 km, measures 7.17 km on the Chinese side and 2.42 km on the Lao section.

The building of the tunnel is a significant step forward in the construction of the China-Laos Railway, said Liu Juncheng of China Railway Kunming Group Co. Ltd., one of the builders of the railway.

Construction has been completed on some 97.5 percent of the designed tunnels on the Yuxi-Mohan section, in the Chinese part of the railway. Track-laying and construction of station are proceeding as planned, Liu added.

Using China's technical standards and equipment, the China-Laos Railway stretches more than 1,000 kilometers from Kunming, capital of southwest China's Yunnan Province, to Vientiane, capital of Laos. The project is scheduled to be completed and opened to traffic at the end of 2021.

The railway is seen as a strategic docking project between the China-proposed Belt and Road Initiative and Laos' strategy to transform from a landlocked country to a land-linked hub. The railway will slash the travel time between Kunming and Vientiane to half a day.