FORT MEADE - US soldier Bradley Manning on Wednesday told a military court "I'm sorry" for giving war logs and diplomatic secrets to the WikiLeaks website three years ago, the biggest breach of classified data in the nation's history.

Private First Class Bradley Manning is escorted into court for the continuation of the sentencing phase in his military trial at Fort Meade, Maryland August 14, 2013.[Photo/Agencies]

"I am sorry that my actions hurt people. I'm sorry that they hurt the United States," the 25-year-old US Army Private First Class told the sentencing phase of his court-martial. "I am sorry for the unintended consequences of my actions ... The last few years have been a learning experience."

Manning spoke quietly and non-defiantly in his first extensive public comments since February.

Manning faces up to 90 years in prison for providing more than 700,000 documents, battle videos and diplomatic cables to WikiLeaks, hurling the pro-transparency website and its founder, Julian Assange, into the world spotlight.

Defense lawyers seeking a milder sentence rested their case on Wednesday after Manning's statement. With about a dozen witnesses including Army superiors, mental health professionals and Manning's own sister, they sought to show Judge Colonel Denise Lind that commanders ignored signs of mental stress.

An Army psychologist testified at the hearing at Fort Meade, Maryland, that Manning, who is gay, felt isolated because he was wrestling with his gender identity. Another mental health specialist testified that Manning had hoped to end war.

"I should have worked more aggressively inside the system ... Unfortunately, I can't go back and change things," Manning, wearing his dress uniform and glasses, his hair in a crew cut, said from the witness stand.

He did not appear to be reading from notes and looked at the judge and around the room as he spoke.

"I understand I must pay a price for my decisions," Manning continued in his first lengthy public statement since February.

"I want to be a better person, to go to college, to get a degree and to have a meaningful relationship with my sister and her family."

Manning was convicted of 20 charges, including espionage and theft, on July 30. He was found not guilty of the most serious count, aiding the enemy, which carried a life sentence.

A military spokesman said the judge would most likely sentence Manning next week at the earliest.

Prosecutors, who have argued that Manning was an arrogant soldier who aided al Qaeda militants and harmed the United States with the release of the documents, will have an opportunity to rebut the defense case on Friday.