Diane Sawyer stepping down from 'World News,' to be replaced by David Muir

Diane Sawyer is stepping down as ABC's evening news anchor, to be replaced by David Muir, the network announced Wednesday. ABC added that George Stephanopoulos will take on a new role as chief anchor for live news events.

ABC said Sawyer, 68, will concentrate on interviews and specials. During her tenure, ABC's "World News" was a steady second to Brian Williams at NBC, although the ABC broadcast has made gains among younger viewers.

"For many years to come Diane will be a driving force at ABC News with her exceptional storytelling genius," ABC News President James Goldston said in a statement. "She will create innovative television specials and events, and, of course, continue to conduct the biggest interviews with the most important and 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 will officially begin his new role on Sept. 2.

Sawyer tweeted about the announcement, congratulating Muir and Stephanopoulos.

Goldston also explained the details of Stephanopoulos' new role.

"In this position, George will be our lead anchor for major special events and breaking news at ABC, driving our live network coverage for the biggest stories," he stated. "The news division could not be in stronger hands with George in his new role."

The Associated Press contributed to this report.