Defense Secretary Robert M. Gates has ordered an investigation to identify sources who leaked information to The Washington Post about a forthcoming Pentagon report on the potential impact of allowing gays to serve openly in the military.

"The Secretary strongly condemns the unauthorized release of information related to this report," Pentagon press secretary Geoff Morrell said in a statement released Friday. "Secretary Gates is very concerned and extremely disappointed that unnamed sources within the Department of Defense have selectively revealed aspects of the draft findings . . . presumably to shape perceptions of the report prior to its release."

The Post reported Thursday that a Pentagon study group has concluded the military can lift the ban on gays serving openly in uniform with only minimal and isolated incidents of risk to the current war efforts. As the basis for the article, The Post cited two anonymous sources familiar with a draft of the report, which is due to President Obama on Dec. 1.

The Defense Department has closely guarded the contents of the report, which has been in the works since March. It includes results of a survey sent to 400,000 active-duty and reserve troops as well as 150,000 military spouses.

The Pentagon did not dispute details reported by The Post, but Morrell said premature disclosure of the study's conclusions risks "undermining the integrity of this process."