The United States warned Ethiopia and Eritrea on Monday against fuelling conflict between a US-backed interim government and extremist forces in neighbouring Somalia as a 'proxy' for their own disputes.
The State Department also called on the powerful Somali Islamic Courts movement not to use the outside interference as an excuse for boycotting negotiations with the transitional government.
State Department spokesman Sean McCormack said Washington had "concerns" over reports of Eritrea providing weapons to the Islamic Courts while Ethiopia is said to have deployed troops in support of the government.
Eritrea, which gained independence from Ethiopia in 1993 after a decades-long guerrilla war, has ongoing boundary disputes with its former master, McCormack said.
"We would hope that states not try to use Somalia as a proxy for any of their disputes," he said.
"It would be rather unfortunate for Somalia, as well as other countries in the region."
US officials have been in contact with all sides to urge "steps to de-escalate tensions as opposed to escalate tensions," he said.
The Somali Islamists on Monday refused to attend a new round of talks with the government in neighbouring Sudan until Ethiopia withdraws its troops from the country.
The Islamist movement has gained control of much of southern Somalia since seizing the capital, Mogadishu, in June and isolating the Western-backed transitional government which has been unable to restore order in the horn of Africa nation.
The two sides agreed tentatively last month to create joint military forces and were due to begin talks on power-sharing and other matters.
They have since split over the issue of deployment a regional peacekeeping force in the country, a plan backed by the government but vehemently opposed by the Islamists.
McCormack criticised the extremists' decision to boycott the latest talks in Khartoum as "unfortunate" and urged them to return to negotiations.
"The political groups in Somalia, including the Islamic Courts and the transitional federal institutions, need to try to come together and have a political dialogue with respect to what is the best future pathway to Somalia -- for Somalia," he said.