On Wednesday the AU also endorsed a plan urging the restoration of state authority in the north of Mali, which is currently under the control of radical Islamists.
The plan also calls for free elections in Mali early next year, and is to be presented to the United Nations Security Council.
The AU announcement late on Wednesday came as the International Committee of the Red Cross warned of a growing food crisis in the north of the country.
"However the armed conflict in northern Mali unfolds, the risk of a further worsening in the humanitarian situation in the region and throughout the Sahel is high," said ICRC president Peter Maurer, just back from a three-day visit to the region.
He also added that help was needed by those fleeing northern Mali to go to the south of the country, or to neighbouring Niger, Mauritania, Burkina Faso and Algeria.
"They need food and better access to clean drinking water and health care," he explained.
Meanwhile, earlier on Wednesday, speaking to Radio France Internationale, France's defence minister appeared to backtrack from a suggestion that military intervention in Mali was imminent, cautioning that preparations to deploy the African force remained at an early stage.
Jean-Yves Le Drian had said last week that military action would happen in "weeks not months".
But he told RFI: "It is not the time for intervention at the moment. Right now it is about putting in place the preparations requested by the UN Security Council."
France has led the push for military action in Mali, a former colony where six French hostages are currently being held by Islamist groups. It has promised to support the African force with training, logistics and equipment.
US Secretary of State Hillary Clinton is due in Algeria next Tuesday, where one of the topics of discussion will be the crisis in neighbouring Mali.
Algeria and Mauritania, which both share borders with the rebel-held north of Mali, have called for dialogue to reach a political solution to the crisis, but both have ruled out sending troops into Mali to battle the Islamist militia.