Sweeney, also co-chair of Disney Media Networks, oversees the ABC broadcast network, ABC Studios and cable networks including the Disney Channels and ABC Family.

The former Fox and Nickelodeon executive joined Disney in 1996 and played a key role in implementing Chief Executive Bob Iger's digital strategy. In 2005, she led negotiations with Apple Inc that enabled Disney to become the first Hollywood studio to license its movies for download from Apple's iTunes store.

On March 3, Disney licensed the digital rights for ESPN, the Disney Channel and other properties to satellite operator Dish Networks Inc, allowing it to become the first pay television operator to distribute TV shows online outside of a traditional TV subscription.

Sweeney, 56, said she wanted to explore a more creative job in the television business.

"There has always been a nagging voice in the back of my head pushing me to step out of the comfort zone of the executive ranks and more directly into the creative arena that enticed me to TV in the first place," she said in a statement. "I finally listened to that voice and thought, ?If not now, when?'"

Iger, in an interview with The Hollywood Reporter, said he had offered Sweeney a multi-year contract extension. "She shocked me by saying she didn't really want to go long, that she was thinking about her life and exploring other things," he said.

Iger said he would look for a replacement quickly, aiming to have someone in place during the TV pilot season that runs through May. "My goal is to do it fast," he said.

The CEO also expressed confidence in ABC Entertainment Group President Paul Lee, who was hired to run the network in 2010. ABC has struggled in the ratings, ranking fourth so far this season among the major broadcasters in overall viewers and in the 18 to 49 age group prized by advertisers, according to Nielsen.

Lee "has got my full support," Iger said, adding that "he and I share the (belief that) we'd love a few more hits at ABC."

"By the way, there are elements of prime time that we're quite happy about," Iger said, mentioning political drama "Scandal" and business reality show "Shark Tank."

(Reporting by Lisa Richwine; Editing by Steve Orlofsky, Nick Zieminski and Cynthia Osterman)

By Lisa Richwine and Ronald Grover

Stocks treated in this article : The Walt Disney Company, Apple Inc., DISH Network Corp