[AP] – Carter initially told troops in Afghanistan that he was open-minded when asked if the Defense Department was planning to remove one of the last gender- or sexuality-based barriers to military service. But defense officials said members of his top brass told Carter that they had serious reservations.

The officials spoke on condition of anonymity because they were not authorized to discuss the matter publicly.

Military officials are reluctant to publicly discuss their opposition, but much of it centers on questions about where transgender troops would be housed, what berthing they would have on ships, which bathrooms they would use, and whether their presence would affect the ability of small units to work well together.

There also are questions about whether the military would conduct or pay for the medical treatment and costs associated with any gender transition, as well as which physical training standards they would be required to meet.

The military has dealt with many similar questions as it integrated the ranks by race, gender and sexual orientation. And in many cases they raised comparable worries about what effect the change would have on the force, including whether it would hinder small units that often have to work together in remote, confined locations for long periods of time.

Transgender people — those who believe their gender identity is different than the one they were born with and sometimes take hormone treatments or have surgery to become their chosen gender — are banned from military service. But studies and other surveys estimate 15,000 transgender people serve in the active duty military and the reserves, often in secret but in many cases with the knowledge of their unit commander or peers.

Carter, who became Pentagon chief just five weeks ago, told troops in Afghanistan last month that the key question should be “are they going to be excellent service members? And I don’t think anything but their suitability for service should preclude them.”

What he didn’t know at the time was that one of the troops in attendance was a transgender individual who is serving with the full knowledge of that person’s commander.