Diplomatic efforts were under way Monday to prevent the border conflict between Horn of Africa neighors Eritrea and Ethiopia from exploding into full-scale war.

African leaders were attending a meeting of the Organization of African Unity in Ouagadougou, Burkina Faso, where finding a peaceful solution to the Ethiopian-Eritrean crisis topped their agenda."The first thing to be done is for Eritrea to withdraw its troops and return to the status quo," Ethiopian Foreign Minister Seyoum Meslin told those at the summit's opening. "(Eritrea) is imposing war on Ethiopia by occupying certain territories."

South African President Nelson Mandela was among those expected at the three-day sum-mit.

The latest border clashes broke out May 6.

U.S. Assistant Secretary of State Susan Rice, who heads the Clinton administration's new African policy, twice rushed to the area to talk peace with Ethiopian Prime Minister Meles Zen-awi and Eritrean President Isaias Afwerki.

Senior U.S. officials have not customarily intervened in African conflicts. But there is concern that a drawn-out conflict between Ethiopia and Eritrea will undermine the U.S.-financed informal alliance of countries headed by former rebels that is the cornerstone of the policy.

A plan devised by the United States and Rwanda calls for Eritrea to withdraw from territory Ethiopia claims. But Eritrea, wedged between northern Ethiopia and the Red Sea, claims it is rightfully occupying territory as defined by boundaries drawn by Italy when it occupied Eritrea in 1885.

Scholars doubt that contested border areas are the real reason behind the conflict. They say the marriage of convenience that brought Isaias' and Meles' rebel groups together to oust Ethiopian military ruler Col. Mengistu Haile Mariam in 1991 has hit the rocks.

Isaias, 51, wants to show his younger colleague Meles, and the world, that he can go it alone and not bow to conditions attached to international aid - especially multiparty democracy.

Isaias heads a highly centralized one-party state and Eritrea's three decades of rebellion have made it relatively self-sufficient, for a poor country with limited resources.

African leaders, including the presidents of South Africa, Djibouti, Uganda and Kenya, called Isaias over the weekend to encourage a negotiated settlement.

Eritrean civilians were hoping to avoid war. Ethiopia's army outnumbers Eritrea's 40,000-strong force by about 3-to-1. Eritrea's tiny air force is no match for Ethiopia's.

In Asmara, Eritreans scanned cloudless skies Sunday and listened for the high-pitched whoosh of the Ethiopian MiG-23 fighters that had bombed their capital's airport Friday and Saturday. But none came.

Skirmishes were reported, however, along the two countries' border. Ethiopia said Sunday it had reoccupied its border town of Zala Anbessa, 65 miles southwest of Asmara, after a daylong battle with Eritrean forces that captured the town last week.

Eritrean troops reportedly had retreated to their side of the border.

Eritrean rebels were instrumental in helping the Ethiopian People's Revolutionary Democratic Front overthrow a 17-year military regime in 1991. Eritrea gained independence from Ethiopia in 1993.

The two countries dispute more than a half-dozen areas along their common border, which was drawn by Italy after it conquered Eritrea.