NTT DoCoMo Inc. will effectively cut its monthly mobile phone fees by adding free calls worth up to 400 yen starting in June, company officials said Tuesday.

The move is in response to an intensifying discount drive by its rival firms.

The wireless arm of Nippon Telegraph and Telephone Corp. will reduce its monthly fees so that it can pass some of its profits onto its customers, the officials said.

NTT DoCoMo will release today its earnings report for fiscal 2000, which ended March 31. The report is expected to show a strong performance.

This effective cut in monthly fees will reduce the company's annual revenues by around 150 billion yen, analysts said.

Under the new fee schedule, NTT DoCoMo will expand its free-call allotment to 600 yen from the current 200 yen for customers paying 4,500 yen a month for the company's Plan A package.

For customers paying 3,500 yen a month for the Plan B option, the firm will increase the free-call allotment from 400 yen to 500 yen.

For customers who pay 4,100 yen for a package offering 1,300 yen worth of free calls, however, NTT DoCoMo will simply reduce the fees charged on each call, the officials said.

NTT DoCoMo reduced its charges by up to 21 percent in December and expanded its so-called family discount to 20 percent from 15 percent in April.