Gay rights groups on Monday called on the military to lift its ban on transgender service members, after new Defense Secretary Ashton Carter suggested over the weekend that being transgender should not alone preclude a person from serving.

“I don’t think anything but their suitability for service should preclude them,” Carter said Sunday during a question-and-answer session with troops in Kandahar, Afghanistan, according to a transcript posted on the Pentagon’s Web site.

Although he has not closely studied the military’s policy, “I come at this kind of question from a fundamental starting point, which is that we want to make our conditions and experience of service as attractive as possible to our best people in our country,” he told the troops. “And I’m very open-minded about — otherwise about what their personal lives and proclivities are, provided they can do what we need them to do for us. That’s the important criteria. Are they going to be excellent service members?”

The response caused ripples within the gay rights community, not only because it came just days after Carter was sworn in, but also because it was viewed as the latest sign that there is a renewed momentum to lift the ban, which remained in place even after the “don’t ask, don’t tell” policy against openly gay troops was lifted in 2011.

During the daily briefing on Monday, White House press secretary Josh Earnest said officials in President Obama's administration "welcome" Defense Secretary Ashton Carter's comments that seemed to express openness to abolishing the ban on transgender Americans serving in the military. (AP)

More than 15,000 transgender men and women serve in the military, according to the Williams Institute, a think tank that studies the gay community. Although “don’t ask, don’t tell” was lifted by Congress, the transgender ban is a policy that could be lifted unilaterally by the Obama administration.

Supporters of the transgender ban have said lifting it could hurt unit cohesion and combat readiness. But gay rights advocates have said it could be lifted without incident, just as “don’t ask, don’t tell” was. They have cited studies that have found that there would be no harm in letting transgender members serve openly and that lifting the policy would not be administratively complicated.

Speaking to reporters Monday, White House spokesman Josh Earnest said President Obama shared Carter’s assessment of how to treat transgender soldiers’ eligibility.

“The president agrees with the sentiment that all Americans that are qualified to serve should be able to serve,” he said.

But even as Earnest said Obama “welcomes” Carter’s comments, he would not explain how that would affect the military’s current policy. “I’d refer you to the Secretary’s office,” he added.

On Monday, a spokesman for the Pentagon said a review began this month of the military’s health policies, including the transgender policy. The routine review will be completed in 12 to 18 months, he said. The last time a review like this took place was in 2011.

Advocates downplayed the significance of the review, saying the military has conducted this same exercise repeatedly and time and again officials have left the transgender ban in place.

“It’s just not enough,” said Allyson Robinson, policy director of SPARTA, a group that advocates for transgender service members. “This is a very specific problem and it needs to be properly addressed by a process that’s proven effective and this one has proven exactly the opposite.”

The remarks were in response to a question posed by Jesse M. Ehrenfeld, a Navy lieutenant commander and physician based in Kandahar, about transgender service in austere environments. In an e-mail, Ehrenfeld said he asked the question because he has treated a transgender service member and interacted with others.

“I am continually struck by how these individuals, who risk their lives every day to support our mission, live not in fear of the enemy, but rather in fear of being discovered for who they are,” wrote Ehrenfeld, an officer for nearly seven years who lives in Nashville with his partner.

Among those present for Carter’s remarks was a transgender service member, according to SPARTA, an advocacy group. The person’s name was not disclosed because coming out could be grounds for dismissal.

“I wanted to tell him I’m one of those people serving in silence,” the service member, who has an enlisted rank, said in a statement issued by the group.  “I love my job, I’m supported and respected by the people I serve with, and I want to make the military a career. But until the regs [regulations] are updated, just speaking up for myself could end it all.”

The exchange came after a period in which many thought that efforts to lift the ban had stalled at the Pentagon, with the snail-like pace of change there and a leadership occupied with military actions abroad. Many advocates worried that time could be running out as the end of Obama’s term approached. Dismissal proceedings continued for service members discovered to be transgender.

Then in December, Air Force Secretary Deborah Lee James suggested that the ban may eventually be lifted. Earlier this month, the military announced it would provide hormone treatment to Chelsea Manning, the former Army private in prison for leaking classified documents. And immediately after being sworn in, Carter appointed as his chief of staff Air Force undersecretary Eric Fanning, who is openly gay.

Gay rights advocates have taken these developments to be a positive sign for their cause, and they pressed the military to go further.

“We urge Secretary Carter to put action to his comments by ordering an immediate review of the outdated regulations that prevent transgender service members from serving our nation openly and honestly,” David Stacy, government affairs director at the Human Rights Campaign, a gay rights organization, said in a statement. “Our nation’s transgender service members bravely and heroically serve our nation, and they certainly deserve to be able to be honest about who they are.”

Staff writer Juliet Eilperin contributed to this story.