A railway line running beneath Mount Everest involving long tunnels through the world's most mountainous terrain is being considered by the government of China.

The bold scheme would link the country with Nepal, in which Everest is located, with a reported finish date of 2020. It would also connect China with India, the other emerging market powerhouse in the region.

A train line running under Mount Everest would be an extension to the existing 1,215 mile-long Qinghai-Tibet route between Tibet and China.

The distinctive topography of the area would affect the maximum speed at which trains could safely travel.

Environmentalists have condemned the plan, with the international Campaign for Tibet warning it contained: "dangerous implications for regional security and the fragile ecosystem of the world's highest and largest plateau"

Rail expert Wang Mengshu told China Daily newspaper: "The changes in the elevation along the line are remarkable. The line is probably have to go through Qomolangma so that worker may have to dig some very long tunnels."

Pundits have predicted the route would deliver benefits for trade and agriculture. But it looks likely to be controversial, not least with India, which claims influence in Nepal. According to State-run Chinese media, the line had been requested by Nepal.

China has been steadily investing billions in Nepal in recent years, adding roads, hydroelectric power stations and telco infrastructure.