KDDI Corp. said Wednesday that it would offer round-the-clock free calls between its fixed-line and mobile phone users beginning Aug. 1, in a bid to gain subscribers from the rival NTT group.

The nation's No. 2 cellular operator, which offers the au mobile phone service, also said it will offer free calls between its fixed-line customers.

"Increasing the number of customers who subscribe to our fixed-line service is our basic strategy. We'd like our au customers to also use our fixed-line services," KDDI President Tadashi Onodera told a news conference.

He said that the new service would reduce KDDI's revenue by ¥2 billion in the current business year to next March, but that its earnings forecast has already taken this into account.