Manning, 25, a former Army intelligence analyst, was convicted July 30.

He was found guilty of 20 of the 22 charges he faced, mostly for espionage, theft and fraud. But a judge found him not guilty of the most serious charge of aiding the enemy, which carries a life sentence.

The 20 charges originally carried the possibility of 136 years in prison, but Judge Col. Denise Lind later granted a defense motion that reduced the potential maximum sentence to 90 years.

At the end of the sentencing phase of the trial, Army prosecutors said Manning should serve at least 60 years in prison. But Manning's defense attorney argued that he should not serve more than 25 years.

In his closing arguments during the two-week sentencing phase, Manning's defense attorney, David Coombs, continued to portray Manning as a naïve young soldier who believed he could change the world.

Coombs said Manning had "pure intentions" in releasing the documents to WikiLeaks. "At that time, Pfc. Manning really, truly, genuinely believed that this information could make a difference."

But in court documents released earlier this week that explained her verdicts, Lind said Manning's conduct "was both wanton and reckless." She added that it "was of a heedless nature that made it actually and imminently dangerous to others."

Manning last week apologized for his actions in a short statement he read during the trial's sentencing phase. "I'm sorry that my actions hurt people," Manning said. "I'm sorry that they hurt the United States.

"When I made these decisions, I believed I was going to help people, not hurt people."

He said he was sorry for the "unintended consequences" of his actions and offered that with hindsight, "I should have worked more aggressively inside the system."

Although he acknowledged that "I must pay a price for my decisions and actions" he also expressed the hope to "return to a productive place in society."

Julian Assange, the founder of WikiLeaks, said Manning's apology was a "forced decision" aimed at reducing his potential jail sentence. In a statement, he said the apology had been "extorted from him under the overbearing weight of the United States military justice system."

The court-martial began three years after Manning was first detained in Iraq for suspicion of having leaked the video of a 2007 Apache helicopter attack that killed several Iraqi civilians. He was subsequently charged with the leak of 750,000 documents that were a mix of U.S. military battlefield reports from Iraq and Afghanistan and diplomatic cables.

The release of the documents has been described as the most extensive leak of classified information in U.S. history.

During the nearly two-month court martial, prosecutors presented detailed computer forensics of Manning's computer activity during his deployment to Iraq in late-2009 to mid-2010. They said the evidence showed that within weeks of his arrival in Baghdad, Manning had begun searching classified military computer networks for materials that were of interest to WikiLeaks.