China will invest US$ 42 billion, to revive a long-stalled plan to build the world's longest undersea tunnel across the Bohai Strait linking the country's eastern and northeastern regions. Deep beneath the Bohai Sea, Chinese engineers may soon begin boring the longest submarine tunnel on the planet. At an estimated 123 kilometers long, it would surpass the combined length of world's two longest underwater tunnels-Japan's Seikan Tunnel and the Channel Tunnel between the UK and France.

The tunnel will run from the port city of Dalian in northeastern Liaoning province to Yantai city in eastern Shandong. Today the drive between Dalian and Yantai takes around seven to eight hours. The Bohai Tunnel would shorten that to an hour.

China announced plans in 1994 to build the tunnel, at a cost of US$ 10 billion, and set to be completed before 2010. But more than 20 years on, the project remains stuck in the planning stage without elaborating.

Currently world's longest undersea tunnel is in Japan. The 54 kilometer Seikan tunnel links Honshu and Hokkaido islands and started operating in 1988 after more than two decades of construction. The Channel tunnel between England and France is about 51 kilometer long.