Seventeen LGBT groups have signed on to a letter spearheaded by the American Civil Liberties Union (ACLU) calling on President Barack Obama to grant clemency to Chelsea Manning.

Manning, a former Army intelligence analyst, is serving a 35-year prison sentence at Fort Leavenworth, Kansas for violating the Espionage Act.

The groups say Manning, who came out transgender on the first day of her sentence, has been mistreated by the Army.

“Manning, a transgender woman who is being forced to serve out her sentence in an all-male prison, has been subjected to long stretches of solitary confinement – including for attempting suicide – and denied necessary medical treatment related to her gender dysphoria,” the letter states. “The Army even opposed her request to use her legal name and to be referred to by female pronouns. While the armed forces have finally opened the door to transgender men and women who wish to serve, the government has continually fought Ms. Manning’s efforts to be treated with basic dignity.”

The 29-year-old Manning has served six-and-a-half years of her sentence.