SAN FRANCISCO (AP) — The United States should join the dozen other nations that allow transgender people to serve in the armed forces, a commission led by a former U.S. surgeon general said in a report released Thursday that concludes there is no medical reason for the decades-old ban and calls on President Barack Obama to lift it.

The five-member panel, convened by a think tank at San Francisco State University, said Department of Defense regulations designed to keep transgender people out of the military are based on outdated beliefs that require thousands of current service members either to leave the service or to forego the medical procedures and other changes that could align their bodies and gender identities.

"We determined not only that there is no compelling medical reason for the ban, but also that the ban itself is an expensive, damaging and unfair barrier to health care access for the approximately 15,450 transgender personnel who serve currently in the active, Guard and reserve components," said the commission led by Dr. Joycelyn Elders, who served as surgeon general during Bill Clinton's first term as president, and Rear Adm. Alan Steinman, a former chief health and safety director for the Coast Guard.

The White House on Thursday referred questions to the Department of Defense.

"At this time there are no plans to change the department's policy and regulations which do not allow transgender individuals to serve in the U.S. military," said Navy Lt. Cmdr. Nate Christensen, a defense department spokesman.

The report says that while scholars have yet to find government documents explaining the basis for the ban, which has existed in medical fitness standards and conduct codes since the 1960s, it appears rooted in part in the psychiatric establishment's long-held consensus, since revised, that people who identity with a gender different from the one assigned at birth suffer from a mental disorder.

The ban also was apparently based on the assumption that providing hormone treatment and sex reassignment surgeries would be too difficult, disruptive and expensive. But the commission rejected those notions as inconsistent with modern medical practice and the scope of health care services routinely provided to non-transgender military personnel.

"I hope their takeaway will be we should evaluate every one of our people on the basis of their ability and what they can do, and if they have a condition we can treat we would treat it like we would treat anyone else," Elders said in an interview with The Associated Press.

The panel's work was commissioned by the Palm Center, a think tank based at San Francisco State that is funded in part by a $1.3 million grant from Jennifer Pritzker, a Chicago billionaire and former Army lieutenant colonel who came out as transgender last year.

At least a dozen nations, including Australia, Canada, England and Israel, allow transgender military personnel. Transgender rights advocates have been lobbying the Pentagon to revisit the blanket ban in the U.S. since Congress in 2010 repealed "don't ask, don't tell," the law that barred gay, lesbian and bisexual individuals from openly serving in the military.

The commission argued that facilitating gender transitions "would place almost no burden on the military," adding that a relatively small number of active and reserve service members would elect to undergo transition-related surgeries and that only a fraction might suffer complications that would prevent them from serving. It estimated that 230 transgender people a year would seek such surgery at an average cost of about $30,000.

Retired Brigadier General Thomas Kolditz, a former Army commander and West Point professor on the commission, said he thinks allowing transgender people to serve openly would reduce assaults and suicides while enhancing national security. Lawyers for Chelsea Manning, the Army private convicted of giving classified documents to WikiLeaks when she was known as Bradley Manning, presented evidence that stress over having to keep her gender identity secret contributed to an irrational belief that she could end the war in Iraq and by leaking the information.

"When you closet someone, you create a security risk, and we don't need another Chelsea Manning," Kolditz said. "If I were a commander, I certainly wouldn't want people in my unit in a position to be blackmailed."

But Center for Military Readiness President Elaine Donnelly, whose group opposed the repeal of the ban on openly gay troops, predicted that putting transgender people in barracks, showers and other sex-segregated could cause sexual assaults to increase and infringe on the privacy of non-transgender personnel.

"This is putting an extra burden on men and women in the military that they certainly don't need and they don't deserve," Donnelly said.

The commission recommends the president issue an executive order instructing the Department of Defense to amend its regulations so transgender people are no longer automatically barred. The Pentagon then would need to develop rules for assigning service members who are transitioning, said Palm Center Executive Director Aaron Belkin.

The Williams Institute, a think-tank based at the University of California, Los Angeles, estimates that the U.S. currently has about 15,500 transgender military personnel, nearly all serving under their birth genders and not transitioning in an appearance-altering way.

Army Reserve Capt. Sage Fox, 41, was one until recently. Following a deployment to Kuwait, Fox started taking female hormones, In November, with her hair getting long and her voice higher thanks to regular sessions with a speech therapist, she notified her battalion commander, whom she says expressed support. At drill time, an announcement was made to 400 colleagues at the B.T. Collins Reserve Center in Sacramento.

For a few days, Fox thought she might escape the ban. But then she was informed she had been placed on inactive status.

"When I transitioned, I wasn't just a good officer, I became a better officer because I didn't have to deal with that conflict anymore," she said.

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Associated Press writer David Crary in New York contributed to this report.