"The vision is you can watch your favorite network's programming on any screen," said Time Warner Chief Executive Jeff Bewkes, one of the plan's most ardent proponents, at a press conference Wednesday. He added that the plan is "not defensive." Mr. Bewkes said in interview he is in talks with other providers, including DirecTV, Dish Network Corp., Verizon Communications Inc. and AT&T Inc., and expects to announce more deals in "days or weeks." A DirecTV spokesman said it will launch a trial this summer. Terry Denson, Verizon's vice president of content and programming, said the company is close to an agreement with Time Warner and other content providers about a similar test. Representatives of AT&T and Dish declined to comment. There are still significant technical and business hurdles to launching such a system. Some cable-network executives say they believe that cable operators should pay extra for putting more programming online. Both Time Warner and Comcast said Wednesday that the system they are pursuing will be interoperable with other companies' systems to authenticate subscribers. There's also a question of whether some media companies will want to sequester their most popular content behind a subscription wall. "People are afraid to go first," said Mr. Bewkes. "We aren't."