Hormone treatment for gender reassignment has been approved for Chelsea Manning, the former intelligence analyst convicted of espionage for sending classified documents to the WikiLeaks website. 

Defense Department officials said Thursday that the hormone therapy was approved Feb. 5 by Col. Erica Nelson, commandant of the U.S. Disciplinary Barracks at Fort Leavenworth, Kansas, where Manning is serving a 35-year sentence. 

The treatment would enable the Army private formerly known as Bradley Manning to make the transition to a woman. Manning changed her legal name in April 2014. 

The officials were not authorized to discuss the matter publicly and spoke on condition of anonymity. The memo approving Manning's hormone treatment was first reported by USA Today. 

Calls to military officials at Fort Leavenworth weren't immediately returned. 

The decision came after a lawsuit was filed in September in U.S. District Court for the District of Columbia. It alleged Manning was at a high risk of self-castration and suicide unless she received more focused treatment for gender dysphoria, the sense of being a woman in a man's body. 

The Army was providing some treatment but not enough, according to the lawsuit, including psychotherapy from a mental health specialist who lacked the qualifications to treat gender dysphoria. The Federal Bureau of Prisons and many state and local corrections agencies administer hormone therapy to prisoners with gender dysphoria, but Manning is the first transgender military prisoner to request such treatment. 

Chase Strangio, an attorney with the ACLU and counsel for Manning in her lawsuit, called the decision an important first step in Manning's treatment regimen. 

"But the delay in treatment came with a significant cost to Chelsea and her mental health and we are hopeful that the government continues to meet Chelsea's medical needs as is its obligation under the Constitution so that those harms may be mitigated," Strangio said in a statement. 

The 26-year-old former intelligence analyst was convicted in August 2013 of espionage and other offenses for sending more than 700,000 classified documents to WikiLeaks while working in Iraq. 

Transgender people are not allowed to serve in the U.S. military, but Manning can't be discharged from the service while serving her prison sentence.