Sprint reportedly agrees to sell 70 percent stake to Softbank

U.S. wireless carrier Sprint Nextel has reportedly reached an agreement to sell 70 percent of itself to Japanese mobile carrier Softbank for $20 billion.

Both companies' boards have approved the deal, which is expected to be announced tomorrow, sources tell CNBC. Under the deal, Softbank will buy $8 billion in stock directly from Sprint, with another $12 billion purchased from existing stockholders.

The tender offer's price per share is reportedly $7.30, a 27 percent premium over the carrier's closing stock price Friday of $5.73.

CNET has contacted Sprint for comment and will update this report when we lean more.

Sprint had previously confirmed that it was in discussions with Softbank regarding a "substantial investment " by the Japanese mobile carrier.

The investment is expected to be a big boost for Sprint, which continues to be mired in red ink. In the second quarter, the company posted a net loss of $1.37 billion, and the financial troubles are expected to present in the third quarter as well.

The increased size achieved by the combined operations could also be a big win for consumers, presumably leading to a better selection of phones, more competitive price plans, and ultimately, better service. In total, it could mean a stronger rival for fellow national carriers Verizon Wireless, AT&T, and T-Mobile USA.

The majority acquisition would be the second major transaction in the mobile industry lately. Earlier this month, Deutsche Telekom announced plans to acquire regional carrier MetroPCS and merge it with T-Mobile. Soon after that deal was announced, reports surfaced saying that Sprint was considering making its own bid for MetroPCS to head off a merger with T-Mobile.

Softbank has nearly 30.5 million subscribers across Japan, making it one of that country's largest carriers. The Japanese mobile carrier currently has more than 177 billion yen (about $2.3 billion) in capital, according to the company's corporate data page.