UNITED NATIONS, March 9 (Xinhua) -- Sudanese President Omar Hassan Ahmed El Bashir replied to a letter sent by UN Secretary-General Ban Ki-moon containing the detailed framework for the hybrid operation agreed between the African Union (AU) and the United Nations, UN spokesperson Marie Okabe said Friday.

    The secretary-general received a reply from President Bashir dated March 6, Okabe told reporters at UN Headquarters in New York, adding that the reply from Bashir includes a 14 page annex in Arabic, which is being translated and will be reviewed along with the letter.

    "The secretary-general will then consult with the Security Council on the next steps," she said.

    Okabe also noted that the letter contains some positive elements, including a strong expression of support for the joint AU-UN efforts to re-energize the political process and some assurances with regard to humanitarian assistance to the people of Darfur.

    But it also contains some elements, which seem to challenge the agreements reached last November in Addis Ababa and Abuja on peacekeeping in Darfur, she admitted.

    In the letter to Bashir from the UN Secretary-General, Ban detailed a proposed UN-AU hybrid force of up to 24,000 personnel to help resolve the deadly conflict in Sudan's Darfur region.

    The United Nations and African Union have concluded that between 19,000 to 20,000 troops, together with 3,700 police officers and 19 formed police units will be required under the present situation on the ground and the two will now proceed to develop detailed operational plans.

    The hybrid force represents the final phase of a three-phase plan agreed to by the United Nation, African Union and the Sudanese government in Addis Ababa, Ethiopia, in November to help end the fighting between the Sudanese government, allied militias and rebels, which broke out in 2003.

    The first phase, a 21-million U.S. dollars light support package already underway, provides for supplying UN military advisers, police officers and civilian officials as well as equipment to the existing under-staffed AU monitoring mission in Darfur (AMIS).