Top executives of DDI Corp. and IDO Corp. indicated Tuesday that they are considering integrating their cellular phone operations to compete against cellular giant NTT Mobile Communications Network Inc., known as NTT DoCoMo.

"No matter how we cooperate in the fields of technology and networks, it is difficult to compete against NTT DoCoMo with separate management," said IDO President Takeo Tsukada. "We share the basic point (that cellular phone management should be integrated)."

However, the two carriers are currently working on internal adjustments and have yet to enter negotiations, Tsukada said. NTT DoCoMo has a commanding share of the cellular phone market with 23.9 million subscribers. Subscribers at DDI and IDO total 8.5 million.

Tsukada made the remarks at a joint news conference with DDI president Akira Hioki, who said it would be natural for the firms to integrate their cellular phone operations.

At the news conference, the two executives announced completion of a joint nationwide network for their latest digital mobile phone service cdmaOne.

IDO is launching the new service, based on code division multiple access (CDMA) technology, in the Kanto and Chubu regions today, while DDI has added the Tohoku region and Hokkaido to its service area, jointly completing the nationwide network for the service.

DDI, the country's second-largest carrier, started the service in the Kansai, Kyushu, Okinawa, Chugoku, Hokuriku and Shikoku regions through its cellular group companies.

The technology developed in the United States enables subscribers to use high-speed data transmission with good sound quality, the carriers said.