Just back from emergency talks in the Mali capital Bamako, Eliasson said there was a "unique sense of common purpose" among all parties involved in discussions to help drive out the rebel militias.

At the talks, the UN, along with the African Union and West African regional bloc ECOWAS, expressed their determination to help Mali "establish constitutional order and national unity to achieve respect of (its) territorial integrity," veteran Swedish diplomat told journalists in Geneva.

One strategy was to try to convince armed groups in northern Mali to "distance themselves from extremist and terrorist groups" who had occupied Mali's north for more than six months.

Eliasson's comments came amid news that the African Union, which suspended Mali after a March coup, had agreed to take it back into its fold in its bid to curb the extremist threat.

The chaos that followed the March uprising gave free rein to a rebellion by Islamic extremists and Tuareg separatists who took over an area the size of France, before the Islamists forced out their former Tuareg allies.

Earlier this month, the UN Security Council passed a resolution pressing African nations to speed up preparations for an international military intervention.

Western powers are helping draw up the plans, which will be presented to the UN in late November, offering logistical support rather than troops to help Mali recover its territory.

"We are in the midst of doing that planning" for a military intervention, Eliasson said Thursday, adding though that "in the meantime we hope for some progress in the political arena."