"Resistance against the invaders is a right and a duty ... but I urge the brothers in the noble resistance and the great Iraqi people to be just and fair," Saddam said in the letter, a copy of which was sent to AFP by his Iraqi lawyer, Khalil Dulaimi.
"I also urge you to forgive those who lost their way ... and keep the door of forgiveness open until the last minute that precedes the hour of liberation," Saddam wrote from prison.
"Do not forget that your goal is to liberate your country from the invaders and their followers and is not a settling of accounts outside this goal," Saddam said.
"Remember that after each war there is peace, after each division there is unity," he said, adding that "victory against the occupation forces is certain".
Saddam insisted on the unity of the Iraqi people.
"We are a united and undivided people ... made up of Arabs, Kurds and various religions and communities," he said.
Saddam also asked the Iraqi people "to forgive those who shed the blood of your sons and brothers, including the sons of Saddam Hussein" -- a reference to Uday and Qusay Saddam Hussein killed in a US raid in 2003.
The letter, which Saddam said he wrote to mark the Muslim holy month of Ramazan, came as the Iraqi High Tribunal in Baghdad was poised to set a date for its verdict in the ousted president's first trial on charges of crimes against humanity.
Saddam faces the death penalty if convicted over the killing of 148 Shiite civilians from the town of Dujail, north of Baghdad, following a 1982 assassination attempt on the then president.

Copyright AFP (Agence France-Presse), 2006