In an effort to promote its mobile Internet service in the U.S.,

NTT DoCoMo

formally announced that it is taking a stake of about 16% in

AT&T Wireless

(AWE)

. The deal is worth about $9.8 billion.

DoCoMo will pay $6.2 billion to AT&T Wireless and another $3.6 billion to the wireless company's parent, battered telecom giant

AT&T

(T) - Get Report

. DoCoMo's acquisition values AT&T Wireless tracking stock at $23.50 per share, a 31% premium to its closing price yesterday.

DoCoMo has experience putting 15 million cell phone users on the Internet in Japan. With the deal, DoCoMo gains a commitment from its new U.S. partner to use the Japanese company's standard for a new set of high-speed phone services.

For its part, AT&T will be able to use the cash from the deal to pay down some of its heavy debt load.

Although DoCoMo shares ended higher Thursday on the

Nikkei 225

amid expectations that the company would announce the deal after the market closed, it has yet to recoup losses it took after initial reports of the move were published last Wednesday.

TheStreet.com

covered what the

deal would mean to both parties in an earlier story.