Diane Sawyer stepping down from ABC's "World News"

ABC says Diane Sawyer is stepping down as its evening news anchor, to be replaced by David Muir.

The network said Sawyer will concentrate on new programming and specials, while continuing to interview "the most extraordinary people in the world."

Muir is familiar to "World News" viewers as a substitute for Sawyer and has traveled around the country for his "Made in America" series. He'll start as anchor and managing editor of "World News" on Sept. 2.

ABC also said George Stephanopoulos, who anchors "Good Morning America" and "This Week," will take on a new role as chief anchor for live news events.

In a news release, Saywer said, "After wonderful years at 'World News' I decided it is time to move to a new full time role at ABC News. I'll be joined by an incredible team of journalists dedicated to enterprise reporting, innovative approaches to breaking news and new ways of thinking about big issues and events around the world."

"I can't wait to continue bringing more of my specials to prime time and appearing on all ABC News broadcasts, as well," she added. "And to my friends and colleagues George and David -- congratulations. I look forward to exciting work together and great times ahead."

Muir called it "an incredibly humbling day."

"On this incredibly humbling day, I think of the 12-year-old boy with a dream of being a reporter and seeing the world. I never could have imagined seeing that world with Diane Sawyer," he said. "On this day I thank her for not only setting the bar for the rest of us, but for being a trusted friend. I cannot wait to begin this new adventure with Diane and with George, whose political brain power and endless curiosity inspire me, and drive us all to be better every day."