China will invest 260 billion yuan, or about $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, state media said on Thursday. The 123-km (76.4-mile) tunnel will run from the port city of Dalian in northeastern Liaoning province to Yantai city in eastern Shandong, the China Economic Net website said. The report did not say when the project will be completed.