NAIROBI—U.S. President Joe Biden is sending his special envoy for the Horn of Africa to Ethiopia amid international alarm at the escalation of a war that has killed thousands and created a humanitarian crisis in one of the world’s poorest regions. White House national security adviser Jake Sullivan, announcing the trip by envoy Jeffrey Feltman, urged Ethiopia’s government and the Tigray People’s Liberation Front (TPLF) to come to the negotiating table after nine months of conflict. “Months of war have brought immense suffering and division to a great nation that won’t be healed through more fighting,” he wrote on Twitter late on Thursday. Prime Minister Abiy Ahmed’s spokesperson did not immediately respond to a request for comment on Feltman’s travel. Abiy’s federal troops and forces from the Tigray People’s Liberation Front (TPLF), which control Tigray, have been battling since November in a war that has killed thousands of people, sparked …