The tribunal's chief investigating judge told a news conference in Baghdad on Sunday that the ousted president had been charged along with three others in connection with the killing of Shia Muslims in the village of Dujail, north of Baghdad, in 1982.
The judge, Raed Jouhi, said court proceedings against Saddam and the others could begin within days. He did not say when the charges had been made.
According to Iraq's justice system, there must be at least 45 days between charges being brought and a trial beginning.
Diplomatic sources in Baghdad said Jouhi was probably referring to pre-trial motions rather than the trial itself when he referred to proceedings beginning within days.
The other defendants are Barzan al-Tikriti, Saddam's half-brother and former head of Iraq's intelligence service; Taha Yasin Ramadan, a former deputy prime minister; and Awad Hamad al-Bander, former chief judge of Saddam's Revolutionary Court.
The Dujail case was expected to be the first for which Saddam would be tried. It relates to the killing of villagers following an assassination attempt against Saddam as his convoy passed through the village, 60km north of Baghdad.