Sprint and T-Mobile may have reached a major breakthrough, as the wireless carriers hammer out merger talks.

Sources told Reuters that the operators are close to agreeing on tentative terms of a deal that would hand T-Mobile parent Deutsche Telecom a majority stake in the combined company, leaving Sprint parent Softbank with a 40 to 50 percent share.

Earlier reports indicated T-Mobile CEO John Legere would be expected to lead the combined company.

SoftBank Founder Masayoshi Son was courting a T-Mobile acquisition three years ago, but dropped the pursuit after receiving pushback from antitrust regulators.

T-Mobile’s recently won 600 MHz spectrum could complement the large amount of 2.5 GHz spectrum Sprint holds, and Wells Fargo Senior Analyst Jennifer Fritzsche said T-Mobile’s low band spectrum could make for a “meaningful opportunity for towers.” More on how the proposed merger could affect the tower sector here.

A deal may be finalized by October, but talks could reportedly still fall through. Due diligence must be completed, and a merger of the third and fourth largest U.S. wireless carriers would face regulatory approval by the U.S. Department of Justice.

MoffettNathanson analysts have pegged the odds of a merger receiving the green light at 50/50.