NANNING, Sept. 22 (Xinhua) -- Nearly 80 percent of the construction of the China-Laos railway has been completed, said Lao Deputy Prime Minister Sonexay Siphandone on Saturday.

The railway will serve as a key infrastructure for the economic corridor between the two countries and help boost trade, investment and tourism, said Sonexay at the China-ASEAN Expo held in Nanning, capital of south China's Guangxi Zhuang Autonomous Region.

With a designed speed of 160 km per hour, the China-Laos railway is expected to be fully operational in 2021.

Ground-breaking ceremony of the railway was held in December 2015, and the construction of the whole route officially started a year later.

China had invested a total of 12.5 billion U.S. dollars in 782 projects in Laos by the end of June this year since 1988, making it the biggest investor in Laos, said Sonexay.

Chinese investments in Laos are mainly focused on infrastructure projects like hydropower plants, highways and power grids, according to the deputy prime minister.