NEW YORK -- ABC says Charles Gibson will sign off from the "World News" anchor desk on Dec. 18.
The 66-year-old Gibson, who announced his retirement in September, has been at ABC News for more than three decades and plans to continue as an occasional contributor.
He will be replaced by "Good Morning America" co-anchor Diane Sawyer.
Gibson has anchored "World News" since 2006, and was a co-host of "Good Morning America" for much of the 20 years before that.
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