U.S. soldier Bradley Manning was sentenced Wednesday to 35 years in prison for giving hundreds of thousands of classified military and diplomatic documents to the anti-secrecy group WikiLeaks, the largest such leak in the country's history.

In a brief hearing, the military judge didn't offer any explanation for the sentence.

The closely watched case has seen the 25-year-old called both a whistleblower and a traitor.

Prosecutors wanted at least a 60-year prison sentence, saying it would dissuade other soldiers from following in Manning's footsteps. The defense suggested a prison term of no more than 25 years so that Manning could rebuild his life.

Manning leaked more than 700,000 Iraq and Afghanistan battlefield reports and State Department diplomatic cables in 2010 while working as an intelligence analyst in Iraq.

He was convicted last month of 20 offenses, including six Espionage Act violations, five theft counts and computer fraud. Prosecutors were unable to prove that he aided the enemy, a crime punishable by life in prison.

Manning has apologized and said he wanted to provoke a debate on the country's military and diplomatic actions.

"I believed I was going to help people, not hurt people," he said last week.

His defense team said he was under severe mental pressure as a young man struggling with gender identity issues at a time when openly gay people were not allowed to serve in the military.

Prosecutors said the leaks endangered the lives of U.S. intelligence sources and prompted several ambassadors to be recalled, reassigned or expelled.

Prosecutors requested a far longer prison term than other soldiers have received in recent decades for sharing government secrets.

Albert T. Sombolay got a 34-year-sentence in 1991 for giving a Jordanian intelligence agent information on the buildup for the first Iraq war, plus other documents and samples of U.S. Army chemical protection equipment. Clayton Lonetree, the only Marine ever convicted of espionage, was given a 30-year sentence, later reduced to 15 years, for giving the Soviet KGB the identities of U.S. CIA agents and the floor plans of the embassies in Moscow and Vienna in the early 1980s.

Amnesty International and the Bradley Manning Support Network have announced an online petition asking President Barack Obama to pardon Manning

Military prisoners can earn up to 120 days a year off their sentence for good behavior and job performance, but they must serve at least one-third of any prison sentence before they can become eligible for parole.

Manning will get credit for about 3 1/2 years of pretrial confinement, including 112 days for being illegally punished by harsh conditions at a Marine Corps brig. His lawyers asserted he was locked up alone for at least 23 hours a day, forced to sleep naked for several nights and required to stand naked at attention one morning.