The third and fourth biggest U.S. wireless carriers, T-Mobile and Sprint, said Sunday they plan to merge, the third attempt they’ve made to join forces against the country’s two biggest mobile device firms, Verizon and AT&T.

The deal, if it happens this time, calls for T-Mobile to buy Sprint for $26 billion in an all-stock deal.

The combined carrier would have 126 million customers, still third in the pecking order of U.S. wireless carriers, but closer to the top two. Verizon has more than 150 million customers, and AT&T more than 142 million.

The latest agreement caps four years of on-and-off talks between T-Mobile and Sprint. Sprint dropped its bid for T-Mobile more than three years ago after U.S. regulators objected and another proposed merger fell through last November.

The new deal could help the combined companies slash costs to make the new business more competitive with industry leaders. But customers could also pay more for wireless coverage because the combined company may not have to offer as many deals to attract new customers.

U.S. regulators at the Federal Communications Commission are expected to take a close look at the merger’s effects on customers and whether the deal violates antitrust laws.
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