France warned that Western forces would be drawn into an offensive against al-Qaeda strongholds in Mali as concerns mount that fundamentalists have established a mini-state.
Laurent Fabius, the French foreign minister, warned that the spread of al-Qaeda allies in Mali could create a base for radical extremists to train and stage attacks on Europe.
The US State Department spokesman added that America was gravely concerned about the Islamist takeover of a vast swathe of territory surrounding Timbuktu.
In a significant shift of French policy, Mr Fabius said that its forces would deploy and spearhead an assault on the area. Al-Qaeda in the Islamic Maghreb (AQIM), an offshoot of the terror outfit, and Ansar al-Dine, a local group, took advantage of a coup and the virtual collapse of the Malian state in January to seize control of the area.
"It's a serious situation because it is the first time terrorists have taken root in important cities and could be in a situation to implant themselves in an entire country," Mr Fabius said. "They have a lot of money, heavy weapons, they are ready to die and their main enemy is France. You have this risk ... and threat that what is happening in northern Mali can happen in other areas."
Mali's fledgling government has sought international backing for a military campaign to retake the territory. Officials said it would ask the International Criminal Court (ICC) to investigate killings, rapes, torture, and attacks on cultural sites in the rebel-controlled north.
The ICC said it was considering investigating rapes and killings that had been committed since fighting erupted in Mali's desert north in January.
President Barack Obama authorised the use of $10 million (£6.5 million) in emergency funds on Thursday for people displaced by the conflict in northern Mali.
The funds will support efforts of the United Nations High Commissioner for Refugees, White House National Security Council spokesman Tommy Vietor said.
Almost 230,000 Malian refugees have fled to Algeria, Burkina Faso, Mauritania and Niger, while an additional 155,000 Malians are internally displaced,