Ethiopia has refused a request by Somalia for military support to fight insurgents, saying such an intervention would need an international mandate, BBC reported.
The Somali authorities have been battling Islamist insurgents who control much of the country.
The speaker of Somalia's parliament had earlier urged neighbouring countries to send troops within 24 hours.
Ethiopian troops helped topple an Islamist movement in Somalia in 2006, but were withdrawn earlier this year.
On Saturday Somali parliamentary Speaker Sheikh Aden Mohamed Nur urged neighbouring Somalia, Kenya, Djibouti, Ethiopia and Yemen to intervene as fierce fighting continued for a second day in the capital Mogadishu.
But Ethiopian government spokesman Bereket Simon said that an international mandate was needed for such an intervention.
He added that the international community, not just Somalia's neighbours, should assist its transitional government.