Mitsui Fudosan Co., the nation's largest property developer by sales, plans to boost its investment in U.K. developer Stanhope PLC as part of its $6.4 billion global expansion plan.

Mitsui Fudosan, which owns 15 percent of the London-based developer, is also in talks with several companies as it seeks to increase footholds in other countries, such as Germany and France, said Hideto Yamada, managing director of Mitsui Fudosan (UK) Ltd. He declined to provide details because the deal has not been made public yet.

"We are comfortable with this partnership and I believe it has been quite successful, so within the near future, we are increasing our commitment," Yamada said in an interview in Tokyo. "Since we are extending our operation in continental Europe, we are keeping a dialogue with potential partners there."