Secretary of Defense Chuck Hagel on Sunday said he was open to reviewing the military's policy on transgender service.

Despite repeal of “Don't Ask, Don't Tell” more than two years ago, transgender soldiers are not allowed to serve openly in the U.S. military.

“I do think it continually should be reviewed,” Hagel told ABC News' Martha Raddatz. “I'm open to that.”

Hagel said the issue of transgender people serving in the military is more complicated than allowing gays to serve openly.

“The issue of transgender is a bit more complicated because it has a medical component to it. These issues require medical attention. Austere locations where we put our men and women, in many cases, don't always provide that kind of opportunity,” Hagel said.

“I'm open to those assessments, because – again, I go back to the bottom line – every qualified American who wants to serve our country should have an opportunity if they fit the qualifications and can do it,” he said.

He added that the issues are “an area that we've not defined enough.”