And then there were three?

Deutsche Telekom has agreed to sell T-Mobile USA to the Japanese parent company of Sprint in a deal that would combine the third and fourth largest wireless companies in the United States under the Sprint brand.

Japan’s Kyodo News Agency said they learned about the buyout agreement from industry sources, but did not reveal any further details.

SoftBank CEO and Sprint chairman Masayoshi Son and his lobbyists have been promoting such a merger for weeks, so the outlines of a deal between the two companies come as no surprise.

Softbank CEO Masayoshi Son

U.S. regulators have repeatedly signaled their discomfort with any merger between Sprint and T-Mobile, however. Both the heads of the Federal Communications Commission and the U.S. Justice Department have repeatedly raised concerns about the emergence of just three national wireless competitors in the U.S.

AT&T is largely responsible for that perception after its failed attempt to buy T-Mobile in 2011. The large breakup fee and spectrum T-Mobile received after the deal collapsed helped T-Mobile relaunch as a feisty competitor that has forced competitors to cut prices. To regulators, it demonstrated the importance of having at least four national competitors, if only to check the dominance of leaders AT&T and Verizon Wireless. Both the FCC and Justice Department fear any additional mergers would lead to increased prices for U.S. consumers.

Son has argued that the four-competitor policy has left AT&T and Verizon dominant against their two much-weaker competitors. An enlarged Sprint would force broadband speeds upwards as a combined Sprint and T-Mobile launch a massive network upgrade that would force prices down.

Both Softbank and Deutsche Telekom seem eager to close a deal. Softbank is already arranging financing for the estimated $50 billion Deutsche Telekom is expected to ask for T-Mobile USA and the German owner of T-Mobile has sought to exit the U.S. market for at least two years, with the proceeds of any sale used to improve its operations in Germany and eastern Europe, where the company has been more profitable.

So far, Wall Street has had only a muted reaction to the merger news. Many analysts still expect U.S. regulators to shoot down any deal that proposes merging any of the four current large wireless carriers.

SoftBank CEO and Sprint chairman Masayoshi Son was interviewed at this week’s Code Conference. On the current state of wireless: “Oh my god, how can Americans live like this?” (1:23)