World leaders vowed to work to stem a food crisis in west Africa\'s Sahel region, where millions risk starvation, but were cautious on sending troops to Mali to root out Islamist rebels. Opening high-level talks on a growing humanitarian and refugee crisis, UN chief Ban Ki-moon Wednesday urged world leaders not to abandon the Sahel which has been hit by regional insecurity, drought and poor harvests. \"The region needs your attention, your focus. Do not abandon it and regret it later,\" Ban said of the vast desert area stretching across nine west African nations, where armed Islamic and rebel groups have moved in. \"The Sahel is at a critical juncture. Political turmoil, extreme climatic conditions and fragile economies are combining to create a perfect storm of vulnerability,\" Ban said. France and west African nations led calls for the creation of an African-led force to help Mali flush out rebels from its northern territory seized in a March coup. Mali\'s Prime Minister Cheick Modibo Diarra officially asked the UN Security Council to agree to \"an international military force, one which would be composed of all those willing and able to help us reconquer occupied territories in the north of our country.\" He described appalling daily atrocities being carried out by the rebels in a region which was \"once a haven of peace and is now a source of threats to international peace and security.\" Chaos erupted in Mali in March when military putschists seized power in the capital, Bamako, ousting President Amadou Toumani Toure, only to see the north and east fall to Tuareg rebels and Islamist militias linked to Al-Qaeda. French President Francois Hollande said his country, the former colonial power, was ready to do \"everything it can to support the troops that are being planned\" and urged a Security Council meeting \"as soon as possible.\" \"It has come time for the international community to take its responsibility to come to the assistance of Mali. The time has come,\" Hollande said. He later said he hoped the force would be set up within weeks. Senegalese President Macky Sall echoed the same concerns. \"The Sahel region has become a subject of great preoccupation for us. It is not just a low-level crisis, nor just a local threat. We need clear military action today.\" But UN Secretary General Ban, who is appointing a special UN envoy for the Sahel, urged caution.  \"Any proposed military solution to the security crisis in northern Mali should be considered extremely carefully,\" he said. \"This could have significant humanitarian consequences, including further displacement and restrictions on humanitarian access.\" The Sahel stretches across a swathe of west Africa, including Burkina Faso, Cameroon, Chad, Gambia, Mali, Mauritania, Niger, Nigeria and Senegal. US Secretary of State Hillary Clinton said work must urgently begin in the Security Council to consider the various proposals because the situation was \"not only a humanitarian crisis, it is a powderkeg that the international community cannot afford to ignore.\" \"For some time, Al-Qaeda in the Islamic Maghreb and other groups have launched attacks and kidnappings from northern Mali into neighboring countries. \"With a larger safe haven, and increased freedom for maneuver, terrorists were seeking to extend their reach and their networks in multiple directions,\" she said. \"They are working with other violent extremists to undermine the democratic transitions underway in North Africa, as we tragically saw in Benghazi,\" Clinton added. This year, more than 18 million people in the region have been hit by a severe food crisis, with some 1.1 million children facing acute malnutrition, according to the UN Office for the Coordination of Humanitarian Affairs. The instability in northern Mali has led 400,000 people to leave their homes, with more than half fleeing into neighboring countries, straining the infrastructure of already poor western African nations. The Economic Community of West African States (ECOWAS) has 3,300 regional troops on standby, but wants UN approval. But aid organizations are wary about pouring troops into the lawless region which has also become a haven for drug-traffickers and money-launderers. \"There is a major risk that military operations in northern Mali would make an already fragile humanitarian situation much worse,\" said Mamadou Biteye, Oxfam\'s West Africa regional director, in a statement.