The top U.N. peacekeeping official, Jean-Marie Guehenno, spoke to reporters in Addis Ababa after meeting with Ethiopian Prime Minister Meles Zenawi.
Mr. Guehenno said both countries have stressed they do not want war, but added "there is always a risk of war by miscalcuation."
On Saturday, Ethiopia said it would withdraw its troops from the border. Eritrea's foreign ministry has dismissed that declaration as "theatrical news manipulation."
Eritrea contends the United Nations has done too little to make Ethiopia accept a final border drawn up by an independent panel.
Tensions rose again last week when Eritrea said Western members of the U.N. peacekeeping mission along the border must leave within 10 days. U.N. leaders rejected that order.