TOKYO (AP) _ Fidelity Investments, the world's biggest mutual fund company, will expand its retail business in the Japanese market starting next month, company officials said Monday.

Word of Fidelity's move came just over a month after Merrill Lynch and Co. unveiled plans to open 30 retail branches throughout Japan as soon as June.

In addition to walk-in branch offices, Fidelity will offer service to customers via telephone _ a rarity in Japan.

The company will make a formal announcement later this month detailing its retail market strategy in Japan.

Fidelity was granted a Japanese securities trading license in June. It began selling mutual funds to Japanese retail investors in December through booths set up at three bank branches in Tokyo.

Many American and other foreign financial companies have begun setting up beachheads in the Japanese market in anticipation of a series of reforms designed to liberalize Japan's financial industry over the next several years.

The deregulation is expected to benefit foreign companies by opening up access to a pool of personal financial assets worth an estimated $9.3 trillion.

``We're focused on providing Japanese investors with more choices and more options to meet their long-term needs,'' said Donna Morris, senior vice president and manager of Fidelity Brokerage Services Japan LLC, a unit of the Boston-based investment giant.