Rakuten Inc.'s mobile phone unit will charge less than half the fees its rivals do for high data usage, hoping to entice subscribers when it launches services next month as Japan's fourth entrant to the market, sources close to the matter said Monday.

The e-commerce giant is considering a price tag of ¥2,980 per month, a move sure to intensify the price war among Japan's wireless carriers, the sources said.

Rakuten will announce a price list for its new services on Tuesday, they said.

NTT Docomo Inc. basically offers a high-data plan for ¥6,980 while the nation's two other major players, KDDI Corp. and SoftBank Corp., each charge ¥7,480 for such services.

Rakuten will launch full-scale wireless communications services in April, becoming the nation's fourth player in the crowded mobile phone market.

Rakuten first entered the mobile phone business in October 2014 as a virtual mobile network operator, using the networks of other wireless carriers.

The company had initially planned to launch full-scale services with its own networks last October but had to push the schedule back because of delays with installing network base stations.

Rakuten's networks are expected to provide services only in selected major cities, such as Tokyo, Nagoya and Osaka.

The company plans to rent KDDI's networks to offer nationwide services, but the fees to its rival could weigh on its profitability, possibly incurring red ink at the outset.

Rakuten Chairman and CEO Hiroshi Mikitani has said the company can provide wireless services at lower prices as it employs new technologies.

The company is also banking that its entry into the mobile phone market will lead subscribers to its other businesses, including online shopping and financial services.