CHICAGO - Oprah Winfrey plans to tell viewers on Friday's live edition of her top-rated daytime program that she will retire the Chicago-based syndicated talk show that made her rich, famous and, if not a kingmaker, a maker of bestselling authors and perhaps even a U.S. President at the end of the 2010-11 season, its 25th on national TV.

Harpo Productions confirmed Thursday both her decision and that she will discuss it on her program, her last live show of the calendar year, set to air at 9 a.m. on WLS-Ch. 7,her flagship station.

Speculation has been rampant that she might choose to leave daytime TV ever since it was announced in January 2008 that she and Discovery Networks planned to partner on a cable network: OWN: The Oprah Winfrey Network.

The cable network's debut, originally set for this year, has been delayed more than once and a launch date is expected to be firmed up by the end of this year for sometime in 2010. The new channel will take the place of what is now Discovery Health, available in 70 million homes from the start.

One problem for the new venture was that until Winfrey completed her commitment to CBS Television Distribution, her syndicator, and the stations that carry her program, she would not be free to do a talk show for the cable channel or give other OWN matters her full attention.

It was at Channel 7, under station boss Dennis Swanson, that her success as host of the local "AM Chicago" program at challenging Phil Donahue, then the nation's top daytime talker, in his home market that helped embolden Winfrey to enter syndication in 1986.

As Winfrey has told the story, Chicago Sun-Times film critic Roger Ebert, who had begin to enjoy success himself with a movie review program he and Chicago Tribune critic Gene Siskel launched, had suggested the move while on a date.