Pvt. Bradley E. Manning, now known as Chelsea and convicted of leaking classified military documents to Wikileaks, will soon be moved to Leavenworth Federal Prison to serve 35 years in an all-male facility as a transgender female.
"I am female," she said in a statement Thursday, asking media and others to use female pronouns to refer to her.
"Given the way that I feel, and have felt since childhood, I want to begin hormone therapy as soon as possible," she said. "I hope that you will support me in this transition."
Manning has declared her intention to begin the gender transition with hormones, but it's not clear how she will manage to do this, because the military does not allow hormone treatment or further surgeries to realize a sex change.
Department of Defense spokeswoman Catherine T. Wilkinson told ABC News today that "there is no mechanism in place for the U.S. military to provide hormone therapy or gender-reassignment surgery for inmates."
But transgender advocacy groups sharply criticized the U.S. Army response, saying health care standards in U.S. federal prisons must be applied in military prisons.
"This is America -- we do not deny health care to prisoners," said Mara Keisling, executive director of the National Center on Transgender Equality.
"The Constitution has a prohibition in the Eighth Amendment against cruel and unusual punishment. Denying health care is cruel and unusual punishment. If an inmate breaks a leg, they have to set it. If you have diabetes, they have to treat it. If you develop schizophrenia, they have to treat it.
And, said Keisling, when an inmate is diagnosed with gender dysphoria, the latest diagnosis for what used to be called gender identity disorder, and there is a recommended course of treatment, "they have to provide that treatment."
"[The military] can argue that transgender-related care is not health care, but that is not a winning argument anymore. The medical profession is unified in the belief that transition-related care for transgender people is legitimate and beneficial health care to treat someone with a serious, underlying condition."
But Department of Defense spokeswoman Wilkinson said that inmates in military correctional facilities are "treated equally regardless of race, rank, ethnicity or sexual orientation. ... [They] are considered soldiers and are treated as such with access to mental health professionals, including a psychiatrist, psychologist, social workers and behavioral science noncommissioned officers with experience in addressing the needs of military personnel in pre- and post-trial confinement."
During Manning's court martial and pre-trial hearings, Manning referred to himself using the female name Breanna. His lawyers argued that his judgment had been clouded by his struggle with gender identity problems. Photos that Manning took of himself dressed as a woman were also used as evidence.
Several court cases have affirmed the right to receive treatment for gender dysphoria in federal prisons.
A federal judge last year ordered the Massachusetts Department of Corrections to provide sex reassignment surgery for Michelle Kosilek, a transgender woman serving a sentence for murder. He ruled that the state had violated the inmates' constitutional rights in denying the surgery.
Rates of incarceration among transgender Americans are significantly higher than for the general population, according to a 2011 National Transgender Discrimination Survey, which found that 16 percent of the nearly 6,500 respondents reported having ever been incarcerated, mostly for less than a year, in county jails.
This far exceeds the 2.7 percent of all Americans who have reported being imprisoned.
A study of California's men's prisons identified more than 330 transgender inmates out of a population of approximately 160,000. All these inmates were transgender women.
In federal prisons, guidelines for housing of transgender inmates in sex-segregated facilities are regulated by the Prison Rape Elimination Law.
Manning's lawyer, David Coombs, said his client's goal was not to be placed in a women's prison. Rather "the ultimate goal is to be comfortable in her skin, and to be the person that she's never had the opportunity to be," according to an interview on the "Today" show.
Coombs said he hoped Fort Leavenworth "would do the right thing and provide" the hormone treatments. If not, he said he would "do everything in my power to make sure that they are forced to do so."
Masen Davis, executive director of the Transgender Law Center in Oakland, Calif., told ABCNews.com that its attorneys were "looking at every recourse that Manning will have in military prison" to obtain necessary medical treatment.
"He has a right to access to care, including a prescription for estrogen," she said. "Medical treatment should be determined by a doctor, and not bias against trans people."
The Washington, D.C.-based Human Rights Campaign also weighed in on the issue with a statement today:
"Regardless of how she came to our attention, Pvt. Chelsea Manning's transition deserves to be treated with dignity and respect," the statement read.
"As Pvt. Manning serves her sentence, she deserves the same thing that any incarcerated person does -- appropriate and competent medical care and protection from discrimination and violence.
"The care she receives should be something that she and her doctors -- including professionals who understand transgender care -- agree is best for her."
ABC News' Luis Martinez contributed to this story.