Tokyo-based mobile carrier Softbank Corp. has reached a deal with Sprint Nextel Corp. to acquire 70 percent of U.S. wireless company Sprint for $20.1 billion in the largest ever foreign acquisition by a Japanese company.

The deal was announced Monday at a joint news conference in Tokyo by Softbank President Masayoshi Son and Sprint Chief Executive Dan Hesse.

The deal, approved by the boards of both companies, still needs approval from Sprint shareholders and U.S. regulators. Softbank said the deal is expected to be completed by the middle of next year.

The deal will bring together the third biggest mobile carriers of both Japan and the U.S., underlining the growth ambitions of Softbank.