bolster the strength of the African-led force in Mali, or AFISMA, and gave member states one week to commit troops to the mission.
"We definitely know, based on the first assumptions... that the force size will have to be significantly augmented," AU peace and security commissioner Ramtane Lamamra told reporters after the security meeting.
Lamamra said AFISMA's strength should be increased "to better respond to the needs on the ground," but declined to give numbers..
The AU will also seek urgent "temporary" logistical support from the United Nations for AFISMA, and ask the UN to "authorise... the immediate establishment by the UN of temporary arrangements that would enable AFISMA to speedily deploy and effectively implement its mandate," according to an AU statement.
The logistical support should include transportation, medicine and field hospitals.
The African-led mission is intended to support the weak Malian army -- boosted by the recent French military intervention -- in its battle against Islamist insurgents who seized swathes of Mali's desert north following a coup last year.
Also high on the summit agenda is the slow progress between the rival leaders of Sudan and South Sudan to implement stalled oil, security and border deals.
South Sudan's president, Salva Kiir, and his northern counterpart Omar al-Bashir met Friday for face-to-face talks ahead of the summit.
The two leaders signed a series of agreements in September that have yet to be rolled out. Kiir blamed the delay on Khartoum after meeting with Bashir.
"We have upheld our side of these agreements. Sudan has not," Kiir told the AU security council.
Other key issues remain unresolved, including the contested flashpoint Abyei region.
The AU's security bloc expressed concern that "despite their engagements and the progress that has been made... significant differences remain, which have stymied progress."
Diplomats said leaders are also expected to discuss recent unrest in the eastern Democratic Republic of Congo, where M23 rebels took over the key town of Goma before pulling out. They have since agreed to negotiations with the Congolese government, but the talks have been dragging.
The AU summit, officially themed "Pan Africanism and African Renaissance", will kick off the 50th anniversary celebrations of the founding of the Organisation of African Unity, the predecessor to the AU.
African leaders are also set to select a new AU chair to replace the outgoing head, Benin's President Thomas Boni Yayi. This post rotates each year on a regional basis.
Ethiopian Prime Minister Hailemariam Desalegn is slated to replace Yayi, according to Ethiopia's foreign ministry.