Photo taken on April 12, 2019 show the construction site of the Pu'er railway station of the China-Laos railway in Pu'er City, southwest China's Yunnan Province,. Linking Yuxi City in Yunnan and the Lao capital Vientiane, the China-Laos railway is expected to be fully operational by the end of 2021. (Photos: Xinhua)

A worker directs a road roller at the construction site of the Pu'er railway station of the China-Laos railway in Pu'er City, southwest China's Yunnan Province, April 12, 2019. Linking Yuxi City in Yunnan and the Lao capital Vientiane, the China-Laos railway is expected to be fully operational by the end of 2021.

Workers remove slag in the Xinping tunnel of the China-Laos railway in Yuxi City, southwest China's Yunnan Province, April 11, 2019. Linking Yuxi City in Yunnan and the Lao capital Vientiane, the China-Laos railway is expected to be fully operational by the end of 2021.

The Monei River bridge of the China-Laos railway is under construction in Pu'er City, southwest China's Yunnan Province, April 12, 2019. Linking Yuxi City in Yunnan and the Lao capital Vientiane, the China-Laos railway is expected to be fully operational by the end of 2021.

The Ganlanba bridge of the China-Laos railway is under construction in Jinghong City, southwest China's Yunnan Province, April 12, 2019. Linking Yuxi City in Yunnan and the Lao capital Vientiane, the China-Laos railway is expected to be fully operational by the end of 2021.

A worker fastens a screw at the construction site of the Monei River bridge of the China-Laos railway in Pu'er City, southwest China's Yunnan Province, April 12, 2019. Linking Yuxi City in Yunnan and the Lao capital Vientiane, the China-Laos railway is expected to be fully operational by the end of 2021.

Worker Wu Yuanbo (R) and colleagues test the compaction degree of the roadbed of the under-construction Pu'er railway station of the China-Laos railway in Pu'er City, southwest China's Yunnan Province, April 12, 2019. Linking Yuxi City in Yunnan and the Lao capital Vientiane, the China-Laos railway is expected to be fully operational by the end of 2021.

The Ganlanba bridge of the China-Laos railway is under construction in Jinghong City, southwest China's Yunnan Province, April 12, 2019. Linking Yuxi City in Yunnan and the Lao capital Vientiane, the China-Laos railway is expected to be fully operational by the end of 2021.

Workers Zhong Qi (L) and Feng Zhuang examine the Monei River bridge of the China-Laos railway in Pu'er City, southwest China's Yunnan Province, April 12, 2019. Linking Yuxi City in Yunnan and the Lao capital Vientiane, the China-Laos railway is expected to be fully operational by the end of 2021.

Laborers work at the construction site of the Monei River bridge of the China-Laos railway in Pu'er City, southwest China's Yunnan Province, April 12, 2019. Linking Yuxi City in Yunnan and the Lao capital Vientiane, the China-Laos railway is expected to be fully operational by the end of 2021.

Photo taken on April 12, 2019 show the construction site of the Pu'er railway station of the China-Laos railway in Pu'er City, southwest China's Yunnan Province,. Linking Yuxi City in Yunnan and the Lao capital Vientiane, the China-Laos railway is expected to be fully operational by the end of 2021.