The African Union (AU) chairman and Benin President Thomas Boni Yayi has appealed to the United Nations Secretary-General Ban Ki-moon to ensure that Ban will express the need of sending an international force to northern Mali in his report to the Security Council, a diplomatic source in Cotonou said on Friday.

The source said that Yayi has asked Ban to give an ultimatum to the armed groups operating in northern Mali to ensure that they conclude any negotiations by the end of December.

"Any climb-down on the need to urgently send an international force to fight against terrorism in northern Mali will be interpreted as an expression of weakness and a victory for terrorists. Such expression of weakness will not serve to improve the world's collective security and risks to bring about a lack of confidence in the international governance that the UN represents through the Security Council," the AU chairman said in a letter addressed to Ban.

In his letter, Yayi reminded Ban of how the African continent was impatiently awaiting a strong message from the international community regarding the efforts to resolve the crisis in the North of Mali.

"Mr. Secretary General, what we should avoid today, is to give an impression that we lack the firmness to deal with terrorists who do not believe in any faith nor obey any law," he said while insisting on the need to put a lot of pressure on the terrorists.

"It's only pressure that will pay off. It's pressure that will force the armed groups to engage in genuine dialogue," the president said in his letter.

He recalled that the strategy for military intervention in Mali was jointly drafted by experts from the UN, the European Union, the African Union and those from the Economic Community of West African States (ECOWAS), and then submitted to ECOWAS presidents for approval, before being sent to AU's Peace and Security Council and finally to the UN Secretary-General.