(Reuters) - Television journalist Diane Sawyer will be stepping down as the anchor of the nightly newscast "ABC World News," but will continue working for the network, doing specials and interviews, ABC News President James Goldston announced on Wednesday.

Sawyer, 68, has held the top news job for nearly five years and has been with ABC since 1989. She will begin her new role later this summer and will be replaced in September by journalist David Muir, who is the network's weekend anchor and works on its news magazine show "20/20."

"As much as she loved leading 'World News' to new heights ... Diane decided that now is the moment to concentrate full-time on tackling big issues in new ways," Goldston said in a statement.

"Diane is one of the giants of modern journalism, and we can’t wait to see where she’ll lead us next," he added.

Sawyer, who started her career in Kentucky and worked as a press aide in the White House during the administration of President Richard Nixon. Before joining ABC, she worked at CBS News, including a stint as a correspondent for "60 Minutes.

Sawyer is the second prominent female journalist to step down at ABC in recent months. Barbara Walters retired from the network in May with a weeklong series of tributes, after a career that spanned more than half a century.

Like Walters, Sawyer paved a path for women in U.S. network television as a co-anchor of ABC's "Good Morning America" show and later on the evening news. She also conducted interviews with world leaders, including Iranian President Mahmoud Ahmadinejad.

Goldston also said that George Stephanopoulos, host of the early news show "Good Morning America" and the Sunday morning news show "This Week," will be promoted to the new role as chief anchor of ABC News, leading special events, breaking news and election coverage.

"He will continue to anchor both shows as he assumes this new and critical leadership role," said Goldston.

Stephanopoulos, 53, served as an aide and policy adviser to President Bill Clinton during Clinton's first term in office. Stephanopoulos worked as a professor and author before joining ABC and becoming the host of "This Week."

As a co-anchor of "Good Morning America" he has seen the show rise to become the most popular early news show, overtaking NBC's "Today," which held the top spot for many years.

ABC is owned by the Walt Disney Co DIS.N.