Army Pfc. Bradley Manning leaving a military court facility in July. (Saul Loeb/AFP/Getty Images)

Pfc. Bradley Manning told a military judge during his sentencing hearing Wednesday that he is sorry he hurt the United States by leaking hundreds of thousands of sensitive military and diplomatic documents to the anti-secrecy group WikiLeaks and he asked for leniency.

“I’m sorry I hurt people. I’m sorry that I hurt the United States,” said Manning, who was convicted last month of multiple crimes, including violations of the Espionage Act, for turning over the classified material. “I’m apologizing for the unintended consequences of my actions. I believed I was going to help people, not hurt people.”

The former Army intelligence analyst, who served at a forward operating base in Iraq, had not previously expressed regret for his actions, and during trial had justified the leak as necessary to spark a debate about the nation’s preoccupation with “killing and capturing people.”

Speaking publicly for only the third time since he was arrested in Iraq in June 2010, Manning said he had been naive. “I look back at my decisions and wonder, ‘How on earth could I, a junior analyst, possibly believe I could change the world for the better over the decisions of those with the proper authority?’” said Manning, who spoke for less than five minutes, often in a quavering voice.

Manning, 25, elected to be tried and sentenced by a judge, not a military jury, and Judge Denise Lind, an Army colonel, will determine his sentence. He faces up to 90 years in prison.

Manning told Lind in an unsworn statement that he understood he would have to “pay a price for my decisions and actions,” but hoped that he would one day be able to attend college and have a meaningful relationship with his sister and her family.

“I know I can and will be a better person,” he said. “I can return to a productive place in society . . . I have flaws and issues that I have to deal with, but I know that I can and will be a better person. I hope that you can give me the opportunity to prove, not through words, but through conduct, that I am a good person and that I can return to a productive place in society.”

Manning’s defense team has presented witnesses in the sentencing phase of the trial at Fort Meade to make the argument that Manning’s psychological problems should have led the military to remove him from Iraq. And they hope the judge will consider that as a mitigating factor when she sentences him.

Earlier Wednesday, Manning’s older sister, Casey Manning Major, described a bleak upbringing in Crescent, Okla. She said she was Manning’s principal caregiver when she was only 11 because both of their parents were alcoholics. As a girl, Major said she would wake up to her brother’s cries, make a bottle for him, rock him and put him back to sleep

She described one incident in which her brother sat in the back seat with his mother as they were driven to the hospital to make sure she was still breathing after she tried to kill herself with an overdose of Valium.

A Navy psychiatrist, Capt. David Moulton, testified Wednesday that Manning’s facial features were indicative of someone who was exposed to alcohol in the womb and he exhibited other symptoms of fetal alcohol syndrome. Major said her mother drank continuously when she was pregnant with her brother.

Debra Van Alstyne, Manning’s aunt, said she hoped the judge would consider her nephew’s “very hard start to life. He’s a good person. He cares about people. He thought he was doing the right thing at a time when he was really not thinking clearly.”

An Army psychologist said that Manning was under intense pressure while serving in Iraq because he was coping with a gender identity disorder in the “hyper-masculine environment” of a war zone. Manning e-mailed the therapist, Capt. Michael Worsley, a photo of himself wearing a blond wig and lipstick, which he also sent to one of his superiors in Baghdad.

In the e-mail, Manning said he was “haunted” by what he called “my problem.”

Moulton said that Manning’s identity issues, in combination with his isolation, narcissism and idealism, may have led him to believe that leaking the documents was the right thing to do.

“He became very enthralled with this idea that the things that he was finding were injustices that he felt he morally needed to right,” said Moulton, who spent 21 hours interviewing Manning at Fort Leavenworth, Kan.