Softbank Corp. said Monday it will acquire a controlling stake in major U.S. cell phone company Sprint Nextel Corp. for 20.1 billion U.S. dollars. The deal will be completed in mid-2013 and Softbank will eventually take a 70 percent stake in Sprint Nextel through the deal. The U.S. mobile phone company will become a Softbank subsidiary, the Japanese firm said. The acquisition by Japan's third-largest mobile phone carrier gives birth to one of the leading communications groups in the world with a combined 90 million mobile phone subscriptions, Japanese media reported. The move comes as mobile companies are investing to boost infrastructure for high-speed data communication using the LTE network service, report said.