Now, AQIM controls Timbuktu and the vast region to its west. The Movement for Unity and Jihad in West Africa controls Gao, the north’s largest town. Ansar Dine, a Tuareg Islamist movement, controls the very north, centered at Kidal.

Although the exact association among the groups is opaque, they often fight side by side. Diplomats express hope that Ansar Dine could be lured to the negotiating table, and possibly some elements in the Movement for Unity and Jihad in West Africa, too, before and during a military offensive.

U.S. diplomats and military officials are buzzing to and from West African and European capitals, trying to finalize an intervention plan.

The West African bloc of nations, ECOWAS, has said it is willing to contribute an intervention force, backed by the African Union, and supported financially and logistically by the U.S. and its allies. The United Nations has asked ECOWAS to submit a viable intervention plan for consideration by late November.

The saber-rattling has been loudest from Europe, led by France, which is unnerved by the close geographical proximity of the new extremist haven – a skip and hop through Algeria and across the Mediterranean.

On Oct. 16, French Defense Minister Jean-Yves Le Drian prompted surprise among diplomats when he said in an interview that an intervention was "weeks, not months," away. The French media later reported that Le Drian had backed away from the comment.

The U.S. has pushed for the more deliberate approach, arguing that northern Mali is a complex mosaic of ethnicities and political interests. The U.S. also wants to see democratic elections lead to a new government, despite the northern crisis.

One major roadblock is the beleaguered Malian military, which is expected to lead any charge north. Yet its command structure is in tatters following the March coup by low-ranking officers, and its reputation is extremely poor after getting chased out of northern Mali with little resistance.

"Quite a lot of training and equipping needs to be done first," said the U.S. diplomat.

That training is expected to take months. Then, planners envision a campaign to retake the north’s major towns, followed by a much more drawn-out battle to slowly drain their presence from the surrounding desert.