Japan’s Softbank this morning confirmed plans to acquire US operator Sprint, taking a 70 percent share in the carrier for US$20.1 billion. Of note, Softbank CEO Masayoshi Son has also refused to rule out the possibility of forging deeper ties in the US market via a purchase of MetroPCS.

The Sprint deal – expected to close in mid-2013 – values Sprint stock at US$7.30 a share, with current shareholders able to receive either cash or one share in the new company. The deal includes US$12.1 billion to be paid to Sprint shareholders and an US$8 billion in new capital for the carrier. Both companies’ boards have approved the deal between the number three operators in Japan and the US.

“Softbank is becoming a top player in the market… we will be the global number three in mobile revenue [after China Mobile and Verizon Wireless],” Softbank CEO Son said in the press conference. Son described the deal as a “compelling market opportunity” for both players, talking up the “commonalities between the US and Japan.”

“There is complementary smartphone and LTE strategies… The smartphone is becoming the core of mobile communication,” Son said, noting that the US is a leader in the field. The US market is a duopoly, though, Son noted, suggesting that Softbank’s influence will enable Sprint to better compete with much larger rivals AT&T and Verizon Wireless.

Son spent a significant part of the press conference addressing concern that the deal will put major strain on its finances. Softbank has net debt of about US$10 billion, while Sprint has debt of US$15 billion. Indeed, a client note from Societe Generale said that adding the US$2 billion net debt of smaller rival eAccess (which Softbank this month agreed to to buy), would raise the new company’s “post-deal gearing levels to unacceptable heights.”

“We are confident this investment will pay off. Sprint is making progress in recovery already. We will put capital and strategy into Sprint,” Son stressed. “We are taking risk here… but Softbank has a proven turnaround and debt repayment track record.”

Son said the format Softbank chose ensures that the company will get exactly a 70 percent stake, as opposed to the uncertainty of a more traditional tender offer. And by not doing a full takeover, Sprint will remain a US public company which will improve its access to capital, Son noted. “I think the deal we announced is more transparent,” Son said.

Sprint’s current CEO Dan Hesse will be the CEO of ‘New Sprint’ – the name for the new venture – and Sprint’s headquarters will continue to be in Overland Park, Kansas.

Hesse said the deal will boost its ‘Network Vision’ project as it seeks to “learn” from Softbank’s own successful LTE deployment in Japan. “It could not be a better time for us to have an infusion of capital at this phase of our network deployment,” he commented, adding that the acquisition will not have any effect on its relationship with Clearwire.

Speculation surrounding the deal emerged last week. Reports Friday suggested Softbank’s ambitions in the US may not stop with just an acquisition of Sprint, following rumours that the Japanese company might use Sprint as a vehicle to buy smaller US mobile provider MetroPCS, which this month agreed to merge with Deutsche Telekom’s T-Mobile USA. During today’s press conference Son didn’t rule out this scenario, stating only: “I would like this partnership to be a success first… I cannot rule out any possibilities.”

Sprint’s Hesse reiterated previous belief that he sees more consolidation ahead in the US market and said the deal gives Sprint an opportunity to take part in that. Hesse said that deals that don’t involve AT&T and Verizon are “good for the industry and good for consumers.”