The satellite television service stopped carrying CBS programming in 18 major markets on Friday night after contract negotiations between the two parties reached an impasse.

Dish customers in cities including New York, Los Angeles, San Francisco, Boston, Chicago, Pittsburgh, Philadelphia and Denver are now left without programming from CBS-owned stations. The blackout includes a few independent stations and several others affiliated with the CW network. If the blackout continues, Dish subscribers will be unable to watch college and NFL football games along with popular series like NCIS, Two and a Half Men and The Big Bang Theory.

In a statement, CBS said it “has been negotiating a carriage agreement with Dish for six months and has already granted two extensions.” But it added that “during this time, Dish has dragged its feet at our many attempts to negotiate in good faith.”

Dish, which said more then two million of its 14 million subscribers were impacted, returned fire, laying blame entirely on CBS and a disagreement over the CBS Sports Channel, which remains available through Dish. With no agreement, Dish argued it no longer had legal rights to carry CBS programming.

“We are disappointed that CBS has chosen to black out their local channels, but remain optimistic that the channels will return quickly as both sides are continuing to work tonight to finalize an agreement,” Dish said in a statement.

CBS is seeking payment from Dish for access to its programming. In messages posted online, CBS encouraged its viewers to pressure Dish into an agreement.

“TAKE ACTION TO GET THE PROGRAMMING YOU PAY FOR BACK ON YOUR TV!” the message said. “Call Dish to demand they give you a rebate and return your favorite programs.”

For it’s part, Dish has its own campaign underway, via the website, Dishisonyourside.com. On it, Dish told its customers that “we are working around the clock and are hopeful that our customers’ CBS local channels will be restored as soon as possible.”

The impasse is risky for Dish, which could stand to lose legions of subscribers who are angry about being unable to watch some of their favorite shows. CBS, meanwhile, is losing out on millions of dollars in fees and ad revenue it would otherwise collect, although the amount pales compared to the company’s overall business.

Dish has occasionally dropped programming of other broadcasters after the two sides could not agree on a deal. For example, it dropped CNN and Cartoon Network from its lineup in October before restoring access a month later after the company reached an agreement with networks’ owner, Time Warner.

(This story has been updated with a response from Dish and additional information)