T-Mobile CEO John Legere speaks at CES. (GeekWire Photo / Todd Bishop)

Sprint and T-Mobile are talking about a merger — again.

Sprint CEO Marcelo Claure.

CNBC and The Wall Street Journal reported Tuesday that the two wireless carriers have resumed merger talks. Shares of Sprint spiked more than 15 percent and shares of T-Mobile were up 6 percent.

T-Mobile and Sprint, the No. 3 and No. 4 U.S. wireless companies behind Verizon and AT&T, have been talking about merging, off and on, for several years. Sprint parent company SoftBank nearly acquired T-Mobile in 2014 but the deal fell through after U.S. regulators expressed concerns.

Merger talks heated up again this past fall and it looked like an agreement was near. But in October the companies confirmed that the merger was off; Sprint CEO Marcelo Claure cited a disagreement over control.

Since the initial round of merger discussions, T-Mobile has surged under CEO John Legere, passing Sprint in 2015 to become the third largest U.S. wireless carrier.

Bellevue, Wash.-based T-Mobile last month said it added another 1.9 million new customers in the fourth quarter, its 19th straight period with more than 1 million net customer additions, bringing its total to more than 72 million customers. Revenue at the company climbed 5 percent to $10.8 billion; profits rose $2.7 billion, up from $390 million a year ago.

The company’s growth has resulted from an aggressive campaign in which the company has branded itself the “Un-carrier,” with new pricing strategies, subscriber benefits and promotions that have forced its rivals to change their own packages and promotions.

Sprint meanwhile has struggled in past years, though shares rose after the company posted better-than-expected earnings in February.

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