Chief prosecutor Jaafar al-Moussawi on Sunday said the new charges, which would be announced in the coming days, would involve Saddam's alleged role in "Operation Anfal", which included the 1988 gassing of about 5,000 Kurdish civilians in the village of Halabja.
In all, Kurds maintain that more than 180,000 of their people were killed in Anfal, which began in 1987 and ended a year later. Hundreds of Kurdish villages in northern Iraq were destroyed and thousands were forced to leave their homes.
Al-Moussawi did not specify when the charges would be filed, but the Iraqi court which handles cases against the ousted ruler announced a press conference for Tuesday.
Under Iraqi law, an investigator reviews allegations against a defendant and forwards a recommendation to another judge, who determines if the evidence warrants a trial. If the second judge finds the evidence compelling, then a trial is set at least 45 days from the date of the referral.
The referral process is tantamount to an indictment.
Eight others are under investigation for their roles in Operation Anfal. They include Saddam's cousin Ali Hassan al-Majid, better known as "Chemical Ali'; Sultan Hashim, the former defence minister; and Saber al-Douri, the head of the intelligence service at the time of Anfal.
Saddam is currently on trial on charges related to the killing of Shias in a crackdown launched in the town of Dujail in 1982.