The United Nations Security Council has approved a peacekeeping force for Chad and the Central African Republic to protect civilians bordering Darfur.
The peacekeepers, made up of European Union troops and UN police, will have the right to use force.
Their aim is to end cross-border incursions into villages and refugee camps by fighters from Sudan.
But a Chadian rebel group has warned that the peacekeepers should not act as an intervention force.
Timane Erdimi, leader of the Rally for Forces for Change, told the BBC his men would resist the troops if they did.
The UN says there are 236,000 refugees from Sudan's Darfur region in eastern Chad and 173,000 internally displaced people.
Under the plan which has been drawn up by France, 3,000 mainly French EU troops and 300 UN police will be tasked with monitoring camps for people displaced by the violence.
Sarkozy's agenda?
Non-governmental organisations have generally applauded French President Nicolas Sarkozy's efforts to get the humanitarian mission to Chad and CAR under way.
But some suspect France of having a hidden agenda in the deployment to two impoverished former colonies.
"France is not the best placed to play peacemaker because historically it has contributed more to war than peace on the continent," said Fabrice Tarrit, the head of Survie, an association that works to end France's support of corrupt and undemocratic regimes in Africa.
Richard Dicker, of New York-based Human Rights Watch, for his part had urged the Security Council to use Tuesday's session to impress on Khartoum "its binding legal obligation to arrest and surrender Ahmed Haroun".
In May, the International Criminal Court in the Hague issued arrest warrants for Mr Haroun, since named as Sudan's secretary of state for humanitarian affairs, and for pro-government Janjaweed militia leader Ali Kushayb.
The two face a long list of charges of crimes against humanity and war crimes in Darfur but Sudan has refused to hand them over.
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