"There was a request to move the ceiling of (8,100 troops) up and many other countries are now ready to send troops. Changing the mandate (to allow Amisom to attack al-Shabab) is still under consideration."
Al-Shabab claimed it carried out the attacks after warning it would punish Uganda and Burundi for their troops' presence in Somalia.
No mandate change
The African Union had pushed for Amisom to be given a licence to hunt the al-Qaeda-linked al-Shabab, who are threatening to fight their way to Mogadishu's presidential palace and take over full control of the country.
But a change of mandate for the force, first deployed in early 2007, would require UN Security Council approval and the summit's final declaration provided no specifics on modified rules of engagement.
Johnnie Carson, the United States's most senior Africa diplomat, told reporters that Augustine Mahiga, the UN special representative for Somalia, had told African leaders he was against allowing the peacekeeping troops to attack al-Shabaab.
Carson said the troops' current mandate could allow them to defend themselves as well as protect the Somali government.
"It was Ambassador Mahiga's view that the mandate that currently exists is sufficiently broad enough to provide the Amisom forces with the capacity to do the job that is required," Carson said.
Yves Sorokobi, the spokesman for the UN secretary-general, told Al Jazeera that the the current mandate is "sufficiently strong".
"After the summit in Kampala, the AU will make a certain number of recommendations on how the mandate can be strengthened and on that basis there will be - here at the Security Council - a review of what's doable [and] what's not doable," he said.
"This will depend on the analysis that the AU will deliver to us. If on that basis we believe that there's reasonable ground to fear that the situation might get out of hand, and that the peacekeeping force needs to be given pre-emptive military options, I am pretty confident that the Security Council will support that idea."
Some countries are against the change of the peacekeepers mandate, citing evidence that Amisom has killed civilians.
They argue such incidents could force Somalis to join al-Shabab and other groups, which control parts of Mogadishu and much of southern Somalia.
Somalia's government is hemmed into a few streets of the capital.
At least 21,000 Somalis have been killed in fighting since the start of 2007, 1.5 million have been uprooted from their homes and nearly half a million are sheltering in other countries in the region.