(Combines results of Softbank and NTT DoCoMo, adds background.)

TOKYO -(Dow Jones)- Japan telecom operators Softbank Corp. (9984.TO) and NTT DoCoMo Inc. (9437.TO) Thursday reported a decline in net profit for the April-June quarter pressured by costs, but they both kept their earnings outlook unchanged for the full year.

Softbank, Japan's exclusive supplier of Apple Inc.'s iPhone, said net profit for the three months ended June 30 fell 29% to Y19.44 billion from Y27.38 billion a year earlier, dented by an increase in corporate tax burden.

But its underlying earnings growth still remains intact, with sales of the iPhone continuing to boost the Japanese carrier's data traffic revenue. Japan's third largest mobile carrier by subscriptions, whose businesses also include Internet services, said its operating profit for the quarter rose 45% to a record Y156.60 billion from Y108.29 billion, while revenue also grew to a record Y700.84 billion, up 5.2% from Y666.33 billion.

NTT DoCoMo's net profit for the April-June period slipped 3.5% to Y142.15 billion from Y147.38 billion as measures to improve mobile communication services inflated its operating cost.

Japan's largest mobile phone carrier by subscriptions said its operating profit declined to Y240.52 billion from Y251.82 billion, while revenue edged up 0.4% to Y1.089 trillion from Y1.085 trillion as use of data transmission services grew.

Both carriers kept their full fiscal year ending March 31 guidance unchanged pinning their hopes on growing use of smartphones by Japanese consumers.

Softbank continues to forecast an operating profit of Y500 billion. The company has not disclosed its projections for its net profit or revenue. NTT DoCoMo forecasts a 0.4% increase in net profit to Y497.00 billion and a 0.7% rise in operating profit to Y840.00 billion.

While fighting the fierce battle for a bigger share in the saturated market, the two carriers continue to put more weight behind their data services to make up for declining revenue from phone calls.

Softbank is taking advantage of its position as the sole carrier for the iPhone and the iPad in Japan. NTT DoCoMo aims to start getting more revenue from each subscriber's data communication use than from voice communication by the end of the current fiscal year.

Softbank said last month the order by the Tokyo Regional Taxation Bureau for a Y26.5 billion extra tax payment was related to Yahoo Japan Corp.'s (4689.TO) acquisition of Softbank's data center and network business unit in February 2009.

But Yahoo Japan, the largest Web portal in the world's third largest search market, remains an important profit contributor for Softbank. For the April-June period, Yahoo Japan booked a net profit of Y21.66 billion, up 13% from a year earlier.

Yahoo Japan said earlier this week it will use Google Inc.'s technology to run its Internet searches. Google is also playing a part in NTT DoCoMo's smartphone strategy. DoCoMo's main smart phone model, Sony Ericsson's Xperia, runs on Android.

Softbank's earnings are based on Japanese accounting standards. DoCoMo reports its results based on U.S. accounting standards.

(Juro Osawa contributed to this article.)

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