African leaders failed Monday to sign a U.N.-mediated peace deal aimed at ending two decades of conflict in eastern Democratic Republic of Congo over concerns about who would command a new regional military force. The agreement was to include the deployment of several thousands of extra soldiers to tackle armed militias in the mineral-rich east. The brigade would fight under the banner of the United Nations Organization Stabilization Mission's "MONUSCO" peacekeeping force. Diplomats at an African Union summit in Ethiopia said the troops would come from the Southern Africa Development Community (SADC), notably Tanzania. Leaders from the Great Lakes region had originally been expected to sign the deal Monday morning in Addis Ababa. Seraphin Ngwej, a senior diplomatic adviser to Congolese President Joseph Kabila, said SADC members had raised questions over who would command the intervention force - SADC or MONUSCO. U.N. Secretary General Ban Ki-moon said he had postponed the signing because of "procedural differences" and stressed there were no fundamental differences on the agreement's content between the eight regional states involved.