The technical analysis conducted by the CIA adds to a growing body of evidence that has led U.S. intelligence to suspect the Iraqi dictator survived the U.S.-led war that ousted him from power.
"Although it cannot be determined with absolute certainty, the CIA's assessment after a technical analysis of the tape is that it is likely Saddam's Hussein's voice," said the official, who spoke only on condition of anonymity.
The speaker said the tape was made on July 20, two days before Hussein's sons Odai and Qusai were killed in a fierce attack on a villa belonging to a Saddam cousin in the northern city of Mosul.
But the U.S. official said it could not be determined from the tape when it actually was made. The official added that the poor quality of the audio recording made it impossible to determine with exact certainty that the voice belonged to Saddam.
The voice on the tape urged all of Saddam's former soldiers to take up arms against the Americans and not to cooperate with the Iraqi army being rebuilt by U.S. occupation forces.
"Today I speak in particular to ... your military honor and appeal to the promise you made to the nation and to the people," the tape said.
The voice urged former soldiers not to lose faith.
"On April 11 and 12, we started to reorganize the (Baath) party and people to resist the enemy, and we were in contact with the men of the armed forces," the voice said. The Americans captured Baghdad on April 9.
"News of you, the men of the armed forces and the Republican Guard, reaches me. I am pleased when I hear that you are carrying out these honorable Jihad operations side by side with the brother Mujahedeen or when you are leading them in" Iraq's many cities.
Saddam credited the United States for telling the truth when U.S. assessments declared that the war was not yet over.
"Yes, this war has not ended. The will of the people, the government, the Baath Party is not broken. Now, with the war not over, the occupation will not be able to stabilize the country with its army which occupies our land. The will of the people will not be subdued by the enemy," the voice said.
His comments came as U.S. forces were attempting to form a new Iraqi army as well as a civil defense militia to work with the Americans.