Vodafone and Japan Telecom plan to form a single company to challenge NTT DoCoMo's dominance of the Japanese market.
Vodafone, which is J-Phone's largest shareholder, is backing a move to merge the three regional businesses of Japan's third largest mobile phone company.
Vodafone and Japan Telecom says the creation of a single J-Phone company will help smooth the launch of 3G mobile phones in Japan and create a strong rival to NTT DoCoMo.
The deal should be finalised by November 1, provided it gains approval from shareholders and regulators. It is not known whether it will lead to any job losses.
Following the merger, Japan Telecom will hold 45.05% of the new J-Phone, Vodafone will hold 39.67% and other shareholders owning 15.28%.
Vodafone's total interest in J-Phone will remain at around 60%, as it will hold 20.3% indirectly through its 45% stake in Japan Telecom, as well as its direct holding.
Vodafone has also nominated Darryl Green as new President of J-Phone, who is currently President of Asia Global Crossing Japan. Vodafone will ultimately be appointing 6 out of 13 members of the Executive Board.
Koichi Sakata, Japan Telecom chairman, says: "I am fully convinced that this integration is the key to a smoother approach towards the launch of next generation mobile phone services.
It will contribute to propelling J-Phone into a strong second position in the Japanese market, thereby establishing a firm rivalry against NTT DoCoMo."
Sir Christopher Gent, Chief Executive of Vodafone says: "This merger will create a stronger national competitor and promises to generate significant synergy
benefits and efficiency gains."