In March, the Hague-based court found him guilty of recruiting and using child soldiers between 2002 and 2003.
"The prosecution will request a sentence in the name of each child recruited, in the name of the Ituri region," he told the court on Wednesday.
However, Associated Press news agency reported that the prosecutor said he would be willing to lessen the sentence to 20 years if Lubanga could offer a "genuine apology" to the children and communities affected by his crimes.
Lubanga protested his innocence and said he had not supported the use of child soldiers.
"I have always opposed such recruitment," he was quoted by AFP news agency as telling the judges during Wednesday's hearing.
His conviction was the first verdict reached by the court since it was set up 10 years ago. It is not clear when the court will pass sentence.
In a unanimous decision in March, the three presiding judges said evidence proved that as head of the Union of Congolese Patriots (UPC) and its armed wing, Lubanga bore responsibility for the recruitment of child soldiers under the age of 15 who had participated actively on the frontline.