This just in. According to a new report out this morning, Softbank, Japan’s third-largest wireless operator, is in talks to buy a controlling stake in Overland, Kansas-based Sprint, the nation’s third-largest carrier. The transaction is said to be worth an estimated 1.5 trillion yen, or $19 billion, and would file as the largest purchase of a foreign company by a Japanese firm.

SoftBank used to be the only official iPhone carrier in Japan until the release of iPhone 4S last November. According to people familiar with the situation, Softbank is aiming to buy all of the outstanding shares in Sprint, which had more than 56 million users at the end of June…

Bloomberg relays a Nikkei report claiming that Softbank wants two-thirds of Sprint, providing these details:

Softbank would provide much-needed financial support for Sprint as the U.S. third-largest carrier tries to compete with bigger rivals Verizon Wireless and AT&T Inc. print would give Softbank a base for entering the U.S. market with a compatible carrier via its joint venture with Clearwire Corp., said Jennifer Fritzsche, an analyst at Wells Fargo Securities LLC.

Softbank and Clearwire use airwaves in the same frequency and the same TDD LTE variant of network technology. CNBC is reporting that Softbank is also expected to buy Clearwire, a wholly-owned Sprint subsidiary. Analysts are unsure about the synergies created with such a transaction.

Should the deal ho through, AT&T will remain the sole major United States carrier not owned by a foreign corporation. T-Mobile, the nation’s fourth-largest carrier, is a wholly owned subsidiary of Germany-based Deutsche Telekom.

Softbank released this statement following the rumored deal:

The story about SoftBank and Sprint Nextel Corporation being reported is based on speculation. We have not announced anything. We do not comment on speculation.

Sprint kinda confirmed that something’s cooking, commenting in a statement that the talks are about a “substantial investment by SoftBank”, but stopped short of providing juicer details.

Although there can be no assurances that these discussions will result in any transaction or on what terms any transaction may occur, such a transaction could involve a change of control of Sprint. Sprint does not intend to comment further unless and until an agreement is reached.

Verizon, the largest telecom provider in the United States, is a joint venture of US-based Verizon Communications and UK multinational mobile network operator Vodafone, which holds 45 percent ownership of the joint venture.

SoftBank was established in Tokyo, Japan on September 3, 1981. In March 2011 the company had a market capitalization of approximately $43.52 billion. Sprint’s current market capitalization sits at about $15.12 billion.

Here’s one of their ads featuring a dog named Otosan, hailed as one of Japan’s most successful advertising campaigns in 2007.

Softbank plays in broadband and broadmedia, e-commerce, Internet, technology services, finance, media, marketing, fixed-line telecommunications, to name a few. It also partners with Japanese subsidiaries of foreign companies, including, Yahoo!, E-Trade, EF Education First and Morningstar.