French and African soldiers serving in the Central African Republic are "overwhelmed" by the "state of anarchy" in the country, U.N. Secretary-General Ban Ki-moon said Saturday — a day after Chadian troops began withdrawing from the peacekeeping mission.

The U.N. Security Council is due next week to approve a 12,000-strong U.N. peacekeeping force for the former French colony. The force will take over authority from African Union troops in an attempt to restore order to the country.

But that force is not expected to arrive until September, stoking fears of a security vacuum as the interim government struggles to control intercommunal violence that has killed more than 2,000 people since December.