Bradley Manning will be sentenced early next week.
The army intelligence analyst faces up to 90 years in a military jail.
The 25-year-old was found guilty last month on 20 counts related to leaking enormous amounts of classified information to the anti-secrecy group, Wikileaks.
On Wednesday, Manning read a short, unsworn statement, apologizing for any hurt done to individuals, and for hurting the United States.
His defense team hopes to mitigate the sentence, says independent journalist, Alexa O'Brien.
O'Brien has been chronicling the Manning case since it began.
Manning and his defense team have been trying to explain his actions by presenting the context of his mental state at the time.
They've portrayed him as deeply troubled, isolated, unsupported and improperly supervised.