Manning, who was convicted on some of the military's charges during a court-martial of leaking scores of classified documents to the anti-secrecy group WikiLeaks, showed an "extreme disregard" for U.S. efforts to combat al-Qaida and other terror groups, the military said.
"There may be no soldier in the history of the Army who displayed such an extreme disregard," Army Capt. Joe Morrow said of the 25-year-old former junior intelligence analyst who was serving in Iraq. "At least 60 years is justified. Pfc. Manning is young. He deserves to spend the majority of his remaining life in prison."
Military prosecutors had first crack during the sentencing phase of Manning's court-martial Monday. His defense team is scheduled to follow.
The maximum prison term Army Col. Denise Lind, who presided over the court-martial, could give Manning is 90 years without the ability to apply for clemency or parole until he begins serving the third count on which he was convicted. That would be a de facto life sentence for the 25-year-old, the Los Angeles Times reported.
Had Manning been convicted of aiding the enemy, the top count on the indictment, he would have faced life in prison without parole.
Defense lawyers called a former psychologist and Manning's sister to testify about his damaged mental state before Manning himself testified and apologized for harming his country. Manning pleaded for parole, asking Lind to let him free so he could "better himself."