Comcast Corp. (Nasdaq: CMCSA) and Charter Communications Inc. are pouring some cold water on the telecommunications industry’s merger mania with an unusual new arrangement.

By agreeing to collaborate on their entry into the mobile market, the cable giants are making life difficult for big competitors such as Verizon Communications Inc. (NYSE: VZ). The companies, which both have deals to buy capacity on Verizon’s network at wholesale rates, also made an unconventional pledge to work together on any transaction with a wireless company in the next year. That means if Comcast decides to acquire, say, Sprint Corp., it’ll need Charter’s consent. Or if Verizon tries to buy Charter, Comcast could block the transaction.

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The cable companies’ alliance puts a damper on what was expected to be a no-holds-barred period of merger activity, now that the industry is emerging from a period of strict antitrust scrutiny under the Obama administration. “What this means to us is that wireless M&A is highly unlikely for both Comcast and Charter for the next year,” said Marci Ryvicker, an analyst at Wells Fargo.

In the short term, Comcast and Charter said their new partnership would allow them to become nationwide competitors with Verizon and AT&T Inc. (NYSE: T) in the wireless business. The joint venture could lead to more innovative products, since engineers at both companies will work closely together, and potentially lower prices for customers by gaining negotiating leverage with Verizon or another wireless operator.

The pact might drive Sprint and T-Mobile US Inc. (NYSE: PCS) into each other’s arms. While it’s possible Charter and Comcast could try to jointly acquire either U.S. wireless provider, such a transaction is more complicated to pull off. Sprint, the fourth-largest wireless carrier, had seen Charter or Comcast as potential alternatives to a merger with No. 3 T-Mobile, people familiar with the matter said last month.

The alliance probably lowers the chances of a wireless acquisition by either cable provider in the near future, though the agreement could be a precursor to the cable industry jointly owning a wireless company down the road. Last fall, Charter’s largest shareholder, John Malone, suggested that cable companies could team up to buy a wireless providers like T-Mobile.

Comcast and Charter could eventually pursue an acquisition of Verizon or even Dish Network Corp. (Nasdaq: DISH), which owns a large amount of wireless spectrum, according Jason Bazinet, an analyst at Citigroup Inc. Jonathan Chaplin, an analyst at News Street Research, said in a note the joint venture could even pave the way for a merger someday between Comcast and Charter. It could also be a threat to AT&T and Verizon by helping cable companies take market share, Chaplin said.

“This is more than two companies just working out an MVNO strategy,” Walt Piecyk, an analyst at BTIG Research, said, using the industry term for cable companies reselling wireless service. “It might be about Comcast and Charter owning or building a wireless business as a combined force under a potentially deal-friendly regulatory regime.”

By agreeing to work together, the cable companies can prevent a situation like the one that occurred in 2014, when Comcast surprised Charter by reaching a deal to acquire Time Warner Cable for $45.2 billion. Charter had made its own offer to buy the company for $37 billion and had held talks with Comcast about dividing Time Warner Cable up as part of that bid.

Both Comcast, the largest U.S. cable operator, and Charter, the second biggest, are seeking new sources of revenue as consumer demand for cable TV packages declines. They also face the long-term threat from wireless companies like AT&T that are building the fifth-generation of wireless services, known as 5G, that could offer blazing-fast internet speeds on consumers’ phones that are competitive with cable operators’ broadband service.

Last month, Comcast unveiled a wireless service that lets people connect using its 16 million Wi-Fi hotspots and Verizon’s cellular network as a backup. It plans to introduce the new wireless service to its customers by early June.

“Obviously, the larger the scale of the footprint, the greater the synergies,” Malone said at Liberty Media’s investor day. “The greater the coverage, the more efficient the brand, the greater the negotiating leverage with whoever the network operator is.”

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