The AP said that adjusting photos and other imagery, even for aesthetic reasons, damages the credibility of the information distributed by the military to news organizations and the public.
"For us, there's a zero-tolerance policy of adding or subtracting actual content from an image," said Santiago Lyon, the AP's director of photography.
Lyon said the AP is developing procedures to protect against further occurrences and, once those steps are in place, it will consider lifting the ban. He said the AP is also discussing the problem with the military.
Col. Cathy Abbott, chief of the Army's media relations division, said the Dunwoody photo did not violate Army policy that prohibits the cropping or editing of a photo to misrepresent the facts or change the circumstances of an event. She did not know who changed the photo or which Army office released it, she said.
Dunwoody was promoted to full general on Friday at a Pentagon ceremony attended by Gen. George Casey, the Army chief of staff.
In the original photo, the general appears to be sitting at a desk with a credenza and bookshelf behind her. Three stars on her uniform identify her as a lieutenant general, her rank before Friday's promotion.
The altered photo, distributed by the Army and run on the AP's photo wire Thursday, shows Dunwoody in fatigues in front of an American flag. Her rank, affixed to the front of a soldier's tunic, is not visible.
"We're not misrepresenting her," Abbott said. "The image is still clearly Gen. Dunwoody."
In September, the AP banned use of a photo of Army Staff Sgt. Darris Dawson, who was killed in Iraq. Dawson's face and shoulders appeared to have been digitally altered.