In a cease-and-desist letter sent to Netflix, Verizon also asked Netflix to provide a list of customers on the Verizon network to whom Netflix delivered the notices and other information or face legal action.

Verizon Communications on Thursday demanded that Netflix immediately stop displaying messages to customers that place blame on Verizon's broadband service for slow delivery of Netflix TV shows and movies.

"Failure to provide this information may lead us to pursue legal remedies,'' Verizon general counsel Randal Milch said in a letter to Netflix general counsel David Hyman.

In mid-May, Netflix started displaying messages on the screen for some customers when a video is buffering that say there is congestion on the network of Verizon or another Internet service providers.

Netflix said on Thursday the messages are meant to provide customers more information about their service, similar to its publication of a speed index that ranks Internet service providers.

"This is about consumers not getting what they paid for from their broadband provider,'' Netflix spokesman Jonathan Friedland said. "We are trying to provide more transparency, just like we do with the ISP Speed Index, and Verizon is trying to shut down that discussion."