The African Union is seeking to bolster the strength of the African-led force in Mali, or AFISMA, and has given member states one week to commit troops to the mission, officials said on Friday.
"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.
Lamamra said AFISMA's strength should be increased "to better respond to the needs on the ground," speaking after a high-level security meeting in the Ethiopian capital.
He said the AU would also seek urgent "temporary" logistical support from the United Nations for AFISMA.
The AU asked the UN to "authorize... the immediate establishment by the UN of temporary arrangements that would enable AFISMA to speedily deploy and effectively implement its mandate," Lamamra said, adding that the measures were necessary to respond effectively to the emergency in the West African nation.
The logistical support the AU sought includes transport, medicine and field hospitals, Lamamra said.
The United Nations has authorised the deployment of a 3,300-strong force under the auspices of West African bloc ECOWAS.
But the involvement of Chad, which has committed up to 2,000 troops and is not an ECOWAS member, means the force could now be much bigger.
France has already deployed 2,300 troops to Mali and defence officials acknowledge the force is likely to exceed the 2,500 soldiers that were initially presented as the upper limit.
The AU urged "member states willing to contribute troops to AFISMA to inform the AU and ECOWAS Commissions within a period of one week" whether they would deploy troops in Mali.
The security meeting took place ahead of Sunday's AU summit, where the crisis in Mali is expected to top the agenda.
France swept to the aid of the weakened Malian army on January 11 as Islamist rebels controlling large swathes of the country's north pushed south towards the capital Bamako, amid rising fears the zone could become a haven for terrorism.
The rebels swept through northern Mali -- taking over key towns Gao, Timbuktu and Kidal -- following a coup last year.
The French-led offensive entered its third week with a strong push into the vast semi-arid zone amid rising humanitarian concerns for people in the area facing a dire food crisis.
African leaders are set to meet Tuesday for a donors conference to drum up further funds for Mali operations.
The meeting will include representatives from the European Union and the UN Security Council.