"The AU is doing a job that the UN is supposed to be doing."
There have been almost daily attacks in Mogadishu, the Somali capital, since government-forces, backing Ethiopian troops, drove out Islamic Courts and opposition fighters.
Hundreds of people have died since the beginning of the year.
The Ugandans are due soon to be bolstered by 1,500 AU troops from Burundi, but the African bloc wants the UN to take over when its mandate expires at the end of this year.
But UN countries at an earlier Security Council meeting in August said they were unwilling to commit to such a move.
The recent extension to the AU mandate was approved by the them in July but needed the authority of the UN Security Council to go ahead.