The warning identifies shopping malls in Los Angeles and Chicago as targets.
ABC's Blotter blog has obtained an FBI bulletin warning law enforcement officers that al Qaeda may be planning a holiday season assault against malls in Los Angeles, California, and Chicago, Illinois.
The alert said al Qaeda "hoped to disrupt the U.S. economy and has been planning the attack for the past two years."
Law enforcement officials tell ABCNews.com that the FBI received the information in late September and declassified it yesterday for wide distribution.
The alert, like similar FBI and Department of Homeland Security terror alerts issued over the past five years at holiday times, raised questions about the credibility of the information.
The bulletin acknowledges that U.S. intelligence officers are uncertain as to whether the information is real, and intelligence officers say there is a concern that it could be "disinformation."
Law enforcement officials at three different agencies told ABCNews.com the FBI alert was based on a source who has proved reliable in the past.
To view the actual warning acquired by ABC, click here .