Japan's top wireless operator, NTT DoCoMo Inc, said it is in talks with some Asian mobile carriers for possible capital investment as it aims to seek growth overseas to counter the maturing cell phone market at home.

DoCoMo's recent foreign investments include a 26 percent stake in Tata Teleservices, India's sixth-largest mobile operator, a 30 percent stake in telecom operator Axiata's Bangladesh unit, and a 16.5 percent stake in Malaysian operator U-Mobile.

Our main target is Asia, and there are some other (promising) countries there. We are in contact (with carriers in those countries), NTT DoCoMo Chief Executive Ryuji Yamada told Reuters in an interview on Thursday without elaborating.

DoCoMo is also seeking technological cooperation, rather than capital ties, with Chinese mobile operators such as China Mobile and China Unicom, Yamada said.

Those are real giants and buying a stake of only a few percent could cost us several hundred billion yen (several billion dollars), and acquiring such stakes would not make much business sense for us, Yamada said.

In a bid to enhance the appeal of its cell phone lineup and better compete with rivals KDDI Corp and Softbank Corp, DoCoMo on Friday plans to launch the first handset in Japan using Google Inc's Android operating system.

On top of the smartphone made by Taiwan's HTC Corp, DoCoMo is considering adding some more Android phones to its handset lineup by early next year, Yamada said.

Yamada added that he has also not given up on the possibility of offering Apple Inc's iPhone to its subscribers.

In Japan, Softbank is the only carrier that offers the popular handsets at the moment.

Softbank, Japan's third-largest mobile carrier, outran its bigger rivals in winning new signups minus cancellations for the 26th straight month in June, helped by the popularity of iPhones as well as an aggressive ad campaign and low-cost price plans.

Following Yamada's comments, shares in NTT DoCoMo closed down 1 percent at 140,600 yen, outperforming the benchmark Nikkei average, which fell 1.4 percent.

(Reporting by Kiyoshi Takenaka, Reiji Murai, Mayumi Negishi; Editing by Joseph Radford)

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