Los Angeles ? Cokie Roberts is leaving her Sunday ABC talk show in the fall, making the announcement as the news division is roiled by reports that the network is hoping to replace Ted Koppel and “Nightline” with David Letterman.

Roberts said she made the decision 18 months ago when she was renegotiating her contract with ABC. She and Sam Donaldson began anchoring “This Week” in 1996.

“We’ve started very preliminary conversations about what other role I might play at ABC,” Roberts said Tuesday. She will also continue reporting for National Public Radio and writing a column and books.

ABC made no announcement regarding Donaldson beyond November. “We haven’t even had an opportunity since Cokie’s announcement late yesterday to speak with Sam about his ideas for the future of the broadcast,” network spokesman Jeffrey Schneider said Wednesday.

Roberts said ending her “This Week” duties will give her more weekend time with her family.

“I have three grandchildren, two of whom are in California and one in London, who I don’t see anywhere near enough,” said Roberts, who is married to journalist Steven V. Roberts.

Roberts, 58, will leave “This Week” after the fall elections and when her two-year contract expires. She’s been with ABC News since 1988.

“She is a remarkable journalist and broadcaster with a large and loyal following,” said ABC News President David Westin. “We’re gratified that she will continue to be an important part of ABC News even after she changes her role.”

With Koppel’s “Nightline,” ABC is displeased with the older-skewing audience and hopes Letterman could bring in a younger following in the late-night slot.

ABC has also been unhappy with ratings erosion for “This Week,” which is regularly beaten by NBC’s “Meet the Press.”

ABC denied a USA Today report that George Stephanopoulos and Claire Shipman had been chosen to replace the 67-year-old Donaldson and Roberts on the show. There were no plans to announce a replacement for Roberts, an ABC News spokesman said Tuesday.

Roberts said she would miss Donaldson. The two replaced David Brinkley as host of the show, which Brinkley launched in 1981.

“Sam and I love working together. That’s really the one real sadness, not working with him every week,” she said.

Roberts is the daughter of the late Rep. Hale Boggs, D-La., a former House majority leader, and former Rep. Corinne “Lindy” Claiborne Boggs, who served nine terms in Congress.

Roberts is working on a book about the women who influenced America’s founding fathers.

Last month, Roberts was in Lawrence, Kan., to receive the William Allen White National Citation at Kansas University.