ABC News' Charles Gibson to retire

Sawyer was the obvious choice for a successor, said Westin. The 63-year-old newswoman has a lengthy resume that includes a stint on "60 Minutes" and competing with Barbara Walters for big news interviews in the 1990s. She's done several documentaries in the past few years, including close looks at poverty in America.

"Diane Sawyer is the right person to succeed Charlie and build on what he has accomplished," ABC News Westin said in a statement. "She has an outstanding and varied career in television journalism, beginning with her role as a State Department correspondent and continuing at 60 Minutes, Primetime Live, and most recently Good Morning America."

Diane Sawyer joined ABC News in February 1989, as co-anchor of Primetime Live. In addition to her Primetime assignment, Sawyer was named co-anchor, with Charles Gibson, of Good Morning America in January 1999.

Prior to joining ABC News, Sawyer spent nine years at CBS News. She was the first woman to co-anchor 60 Minutes. Prior to that, she co-anchored the CBS Morning News and was CBS News' State Department correspondent.

Her departure leaves a hole at ABC's "Good Morning America," where she was the show's centerpiece and co-host with Robin Roberts. ABC had no immediate announcement on what will happen on that show, though in-house candidates like Bill Weir and Chris Cuomo would be prospects to take a larger role. Morning news is dominated by NBC's "Today" show, but a further slip from its second-place status would be costly for "GMA" and its parent Walt Disney Co.

Gibson's biggest impact at ABC has been when he stepped into the breach during times of need.

He spent 11 years as co-host of "Good Morning America" before stepping down in 1998. But with the program imploding in the ratings, David Westin asked him to come back and team with Sawyer. What was envisioned as a stopgap of a few months lasted until mid-2006.

After Peter Jennings died of cancer in 2005, Westin replaced him with an anchor team of Woodruff and Vargas. But after Woodruff was seriously hurt in a wartime injury and Vargas became pregnant, Gibson was asked to take over.

"What I value the most is that he really did bring a sense of calm and stability to a broadcast that really needed it," Westin said.

Gibson's wife, Arlene, had recently retired as a school administrator and Gibson's only grandchild had moved with his daughter and son-in-law to Seattle over the past year.

"This has not been an easy decision to make," Gibson said. "This has been my professional home for almost 35 years. And I love this news department, and all who work in it, to the depths of my soul."