The US has urged Ethiopia not to send its troops back into Somalia.
The senior US official for African policy Johnnie Carson told Reuters news agency such a move would be against the interests of both nations.
Ethiopia invaded Somalia in late 2006 to topple an Islamist movement in the capital Mogadishu, sparking an insurgency which is still raging.
Ethiopian troops pulled out in January but witness say their forces continue to make regular incursions.
"The Ethiopian government continues to look very closely at developments in Somalia," said Mr Carson before a scheduled trip to Addis Ababa on Monday.
"Given the long-standing enmity between Somalis and Ethiopians, I will encourage the Ethiopians not to re-engage in Somalia," he said.
He said such a move could prove "counterproductive" for Somalia's fragile transitional government.
Ethiopia's troops invaded in 2006 in support of the transitional government after Islamist rebels had declared a jihad on Ethiopia.
The US allied itself with Ethiopia and is widely reported to have provided Ethiopian forces with intelligence support during the conflict.
Since Ethiopian forces pulled out, Somalia's long-running civil war has continued apace.
Since May more than 165,000 people have fled Mogadishu amid fighting between Islamists hardliners and government forces.
The African Union has 4,300 soldiers in Mogadishu attempting to protect the capital.
Africa backs Somalia troops plea
The African Union has supported the Somali government's request for its neighbours to send troops to help it fight Islamist insurgents.
Ethiopia has said it would need an international mandate before its soldiers would return to Somalia.
A BBC correspondent in Ethiopia says it remains to be seen whether the AU's statement will be enough.
Somalia's speaker of parliament at the weekend admitted the government had been "weakened" by Islamist insurgents.
Last week alone, the security minister, Mogadishu's police chief and an MP were killed.
An alliance of militant Islamist hardliners controls much of southern Somalia.
Speaker of parliament Sheikh Aden Mohamed Nur on Saturday said there was a "state of emergency" and asked for support within 24 hours.
He said that the radical Islamist group al-Shabab, which is accused of links to al-Qaeda, was using foreign fighters.
But al-Shabab says the suicide bomber who killed Security Minister Omar Hashi Aden and at least 34 others in Beledweyne on Thursday was a Somali man and named him as Mohamed Deerow Sheikh Adam.
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On Monday, AU Commission Chairman Jean Ping said in a statement that the Somali government "has the right to seek support from AU members states and the larger international community."
The African Union has some 4,300 peacekeepers in Mogadishu, but their mandate prevents them from attacking the Islamist hardliners except for in self-defence.
The BBC's Elizabeth Blunt in Addis Ababa says Ethiopia troops did fight the insurgents and so all eyes are on Ethiopia to see if it will respond.
On Sunday, Ethiopian Information Minister Bereket Simon said: "Any further action from Ethiopia regarding Somalia will be done according to international community decision."
Ethiopia's troops left Somalia in January under a UN peace deal after spending two years battling insurgents in the country.
Somalia has been without an effective government since 1991. Its UN-backed transitional government controls only parts of Mogadishu, but little of the rest of the country.
Some four million people in Somalia - or about one-third of the population - need food aid, according to aid agencies.
BBC
