NBCUniversal Chief Executive Stephen Burke said he was “surprised” at announcements by HBO and CBS that they will start subscription streaming services, noting that television groups face tough challenges with the efforts, reports The New York Times.

Burke said HBO risks “cannibalizing” its existing business, given that the premium channel would have a tough time not pulling from the base of its current customers, who get HBO through cable or satellite subscriptions.

“I don’t think distributing to consumers via the Internet is an easy thing to do,” Burke said Thursday on a conference call. “I think it’s a voyage that, if you’re successful like Netflix, can be a way to create a lot of value, but it’s not an easy thing to do.”

NBCUniversal is a unit of Comcast, the cable and entertainment giant.

The Times adds: “In recent days, questions about the health of the cable business have loomed over Comcast and its rivals after the announcements by both HBO and CBS. The introduction of these new options for watching TV has caused concerns that more people will cancel their cable subscriptions, or never subscribe at all, because they would be able to watch the shows they wanted to watch — when and how they wanted to watch them — via the Web.”

Stephen Burke