WASHINGTON (Reuters) - U.S. soldier Chelsea Manning, serving a 35-year prison term for passing classified files to WikiLeaks, ended her hunger strike on Tuesday after the Army said she would be allowed to receive gender transition surgery, the American Civil Liberties Union (ACLU) said.

The 28-year-old Army private, who was born male but revealed after being convicted of espionage that she identifies as a woman, announced the hunger strike on Friday.

Manning's treatment will begin with the surgery that was recommended by her psychologist in April, the ACLU, which represented Manning, said in a statement. Manning is held in Kansas.

No transgender inmate has ever before received gender affirming surgical treatment in prison, the ACLU said.

"I am unendingly relieved that the military is finally doing the right thing. I applaud them for that. This is all that I wanted — for them to let me be me," Manning said in a statement, though she went on to criticize the government for taking "so long."

A spokesman for the defense department said it would not comment on the matter in order to protect patient confidentiality.

Manning in July tried to commit suicide over what her representatives said was the government's denial of appropriate treatment for her gender dysphoria, a condition in which a person feels their physical gender is the opposite of the one he or she identifies with.

The Army announced later that month that it would investigate Manning for misconduct in connection with the attempt to take her own life, a probe that could lead to indefinite solitary confinement, reclassification into maximum security or additional prison time.

According to Manning's representatives, doctors have recommended that as part of her treatment for gender dysphoria the soldier, who began hormone therapy in 2015, be allowed to follow "female hair grooming standards."

ACLU staff attorney Chase Strangio said in Tuesday's statement that the government plans to still enforce the male hair standards.

Manning, a former intelligence analyst in Iraq, was sentenced in 2013 to 35 years in prison after a military court conviction of providing more than 700,000 documents, videos, diplomatic cables and battlefield accounts to the anti-secrecy group WikiLeaks. The case ranked as the biggest breach of classified materials in U.S. history.

Among the files Manning leaked in 2010 was a gunsight video of a U.S. Apache helicopter firing on suspected Iraqi insurgents in 2007, an attack that killed a dozen people, including two Reuters news staff.

(Reporting by Eric Beech in Washington and Curtis Skinner in San Francisco; Editing by Mohammad Zargham and Andrew Hay)