Japan and South Korea, long at odds over their wartime history, should be linked by a railway tunnel under the sea symbolising peaceful ties, a group of Japanese lawmakers was reported as saying on Friday.

The cross-party group of parliamentarians is proposing a 128 km (80 miles) tunnel that would be part of a rail link between Karatsu on Japan's southwestern island of Kyushu and Pusan in South Korea via two Japanese islands, Kyodo news agency said.

The tunnel - which would be more than twice as long as the Channel Tunnel connecting Britain and France - could one day allow passengers to travel by rail from Tokyo to London, Kyodo quoted lawmakers as saying.

"This is a dream-inspiring project," Kyodo quoted former defence chief Seishiro Eto as telling reporters after a meeting with other interested lawmakers from various parties. "We'd like to promote it as a symbol of peace-building."

The lawmakers' group first plans to try to persuade Tokyo and Seoul to fund a feasibility study, Kyodo said.

Eto was not immediately available to comment on the report.

Relations between Tokyo and Seoul have improved since former Japanese Prime Minister Junichiro Koizumi stepped down in 2006. Koizumi irritated Asian nations with annual visits to a war shrine that critics see as a symbol of Japan's past militarism.

Conservative South Korean President-elect Lee Myung-bak was born in Japan and is seen as Tokyo-friendly. Japanese Prime Minister Yasuo Fukuda plans to attend his inauguration in Seoul later this month.