African, Arab, European and U.N. leaders agreed in principle Thursday to a joint African Union-United Nations peacekeeping force for Sudan's Darfur region. Representatives from Sudan said they needed to consult with their superiors in Khartoum before the government -- which has strongly opposed allowing U.N. troops in the country -- could give its approval. The force could be as large as 27,000 troops, including the existing 7,000-strong African Union peacekeeping force in Darfur. But the leaders did not lay out a timetable for the force to begin work, partly because Sudan had reservations, the Associated Press reported. U.N. Secretary-General Kofi Annan said additional personnel could include as many as 17,000 soldiers and 3,000 police officers. "The next step is for the U.N. and AU to call a meeting of the non-signatories (of the Darfur Peace Agreement) ... and the government of Sudan. It should take place in the next couple of weeks to resolve outstanding issues by the end of the year," Annan said.