AU leader Macky Sall listed the asserted failings of the UN Security Council and the G20 group of major economies as he noted the problems facing Africa, from jihadism, climate change and health crises to the impact of war in Ukraine and a spate of coups.
"You have to admit that the picture is not pretty," Sall told the opening of the Dakar International Forum on Peace and Security.
Sall said multilateralism had to "serve the interests of all" or else face the "loss of legitimacy and authority."
"The inertia of the Security Council in the fight against terrorism in Africa carries with it the breakdown of the multilateral system," the AU chairman warned.
"Faced with terrorism, the United Nations' classic operations have shown their limits," he added.
"Terrorism which is gaining ground on the continent is not only an African affair, it's a global threat," he told the annual forum, the theme of which is "Africa in the face of external shocks: stability and sovereignty challenges."
"We need to change the doctrine of peacekeeping operations," Sall added, "which have to be modernised to take full account of terrorism, including in Africa."
Sall said he was not glossing over problems "whose solutions are our responsibility," referring to a series of military coups that have shaken West Africa in recent years.