His comments in Tokyo speech came after news reports said News Corp. and the Japanese Internet services company would announce the launch of a Japanese MySpace service as early as this week.
Sources quoted by the Japanese financial newspaper Nihon Keizai say Softbank and News Corporation plan to each provide half of the approximately 1 billion yen (US$8.48 million; euro6.65 million) investment to form a new company.
The new firm, the sources reportedly say, will be called MySpace Japan and will operate the new site.
Kyodo News agency carried a similar report, also without identifying its sources.
Nihon Keizai says Softbank Corp. President Masayoshi Son and News Corp.'s Chairman Rupert Murdoch are expected to hold talks soon to finalize the arrangement.
Softbank official refused to comment on the reports.
News Corp. became the owner of MySpace in 2005 when it bought Los Angeles-based Intermix Media Inc. for US$580 million.
The new venture comes amid rapid growth in Japan's social networking sites, which are thought to have more than 10 million users, the Nihon Keizai said.
Softbank hopes partnering with News Corp. will help it expand its own business, the paper said. Softbank subsidiary Yahoo Japan Corp. provides social networking sites, but Softbank has not involved itself in the sites' operations, the paper added.
Softbank is Yahoo Japan's largest stockholder, with 41.9 percent of the company's shares. Sunnyvale, Calif.-based Yahoo Inc. owns 33.4 percent of the remaining shares.