The result is that around 20,000 Comcast broadband or telephone customers in the Chicago area have seen service disruptions, a Comcast spokesman said. Comcast was seeking a restraining order against AT&T, but had not obtained one as of Wednesday evening.

An AT&T spokesperson said Wednesday that Comcast's suit lacks merit and that the company intends to vigorously fight it. "AT&T is pleased to bring Illinois consumers a new choice for video services as we have in other states and will oppose Comcast's efforts to thwart that," the spokesperson said.

Both companies use the same coaxial cable to deliver the services into people's homes. But Comcast alleges that AT&T installs U-verse improperly, causing service disruptions for customers who subscribe to both Comcast and AT&T. Some consumers subscribe to Comcast for Internet access or phone access, but AT&T for its new television service. The glitch reportedly affects not just the customers who have signed up for U-verse, but all of Comcast's customers within the node.

The spokesman said that AT&T has been "unresponsive" to informal requests to fix the problem, so it sought a restraining order against the company in court. "AT&T has been aware of this problem for more than a year and yet they have been unresponsive and have no sense of urgency in addressing or fixing it. We would prefer to work with AT&T to resolve this issue privately," Comcast stated.

AT&T Monday said it intends to expand its U-verse rollout in Illinois, and will spend more than $1.3 billion on the program in the state.