China is considering a high-speed railway going across Siberia and Bering Strait to Alaska, Canada and the United States, making it the longest railway line in the world.

In a not so distant future, the report says, one might take the train between the 2 countries on a high-speed line straddling two continents. With a proposed average speed of 350 kilometers per hour, passengers would be able to make the 13,000-kilometer journey in less than two days.

Wang Mengshu, railway expert and member of the Chinese Academy of Engineering, planned a route going from an unspecified location in north-eastern China, through eastern Siberia, across Bering strait dividing American and Russian soil, past Alaska onto Canada and southward to mainland US. The project, if undertaken, would be entirely funded by the Chinese government and constructed by Chinese contractors.

The sheer length of the journey would make it the longest railway line in the world, almost 3,800 kilometers longer than the Trans-Siberian railway.

But the largest challenge for the proposed railway construction would be crossing Bering Strait. The massive undertaking of engineering would require an undersea tunnel at least 200 kilometers in length in some of the coldest waters on earth, just south of the Arctic Circle.

If constructed, it would be the world's longest undersea tunnel by far, four times the length of current record-holder the Channel Tunnel connecting France and the United Kingdom.

China has experience with undersea tunnels, notably the 8.7-kilometer long traffic tunnel connecting Fujian in mainland China to Xiamen Island, which opened in 2010.

Another previously planned tunnel is the Taiwan Strait tunnel, which is still pending approval from the Taiwanese side. The tunnel would be 122 kilometers in length, would cost an estimated USD 65 to USD 81 billion, and would connect Taiwan with mainland China as part of the partially completed G3 Beijing-Taipei expressway.

Despite approval by Chinese authorities and widely publicized lobbying for its construction, however, the China-Taiwan tunnel is unlikely to ever be made due to outspoken resistance from Taiwanese authorities, insistent on their continued independence from mainland China.

Since June 2013, Chinese officials have been testing the first intelligent high-speed trains by CSR Qingdao Sifang Locomotive Company Limited. The train features capabilities such as self-test, self-diagnosis and intelligent decision-making intended for safe use in complicated environments. There is no official confirmation, however, if the train would be intended for use in the planned China-US line.