Photo/IllutrationKDDI Corp., one of Japan's three major cellphone carriers and the operator of the au service, announces new rates on May 13 in Tokyo’s Minato Ward. (Ryo Inoue)

Telecommunications giant KDDI Corp. announced it will cut fees by up to 40 percent, taking up the challenge thrown down by rival NTT Docomo Inc. in April.

The firm, which operates the au mobile service and is one of Japan's three major cellphone carriers, unveiled a list of new rates on May 13 that start in June.

KDDI’s move is seen as an attempt to catch up with NTT Docomo, the nation's largest carrier, which in April debuted a plan to offer a communication fee reduction of up to 40 percent from June.

Carriers used to give customers a deep discount on purchasing mobile phones on the condition that they also sign up for a long-term communication plan with the carrier.

This “package sale” strategy has kept communication fees high.

Chief Cabinet Secretary Yoshihide Suga ignited calls for discounts in August last year when he said that Japanese carriers had enough leeway to reduce their fees by about 40 percent.

As a result, a revision of the Telecommunications Business Law was passed on May 10 at the ordinary Diet session with package sales expected to be prohibited in autumn.

The announcements by Docomo and KDDI are part of the firms' strategies to deal with changes in the industry.

In anticipation of the arrival of 5G mobile phones, KDDI will also make an unlimited data usage plan available this summer.

A SoftBank Corp. official said the carrier plans to “make fine adjustments” and will consider slashing communication fees as well.