Mortars have pounded the lawless Somali capital, Mogadishu, as Islamic militias and secular gunmen clashed for a seventh consecutive day.
More than 140 people have died in the past week of fighting, as Islamic militias and an alliance of warlords battle for control mainly in the northern Sii-Sii neighborhood.
Most of the dead are civilians, and thousands of residents have fled the city.
Somalia has been without an effective central government for 15 years and has long been viewed by Washington as a possible terrorist haven.
Many Somalis, including the interim president Abdullah Yusuf Ahmed, say the warlord alliance has U.S. support, a belief that has fueled anti-American sentiment in Mogadishu.
U.S. officials have declined to comment on any relationship with the warlords.
The U.S. officials say they are working with many Somalis to support the establishment of the interim government.