A decade ago Ethiopian Prime Minister Meles Zenawi and Eritrean President Isaias Afwerki launched a border war in the Horn of Africa that killed 80,000 people.

As I left meetings with their top advisors in Asmara and Addis Ababa a few weeks ago, I could not help feeling that neither side seemed willing to admit that they once again have set in motion forces that could lead to another bloody battle in one of Africa's poorest and most conflict-ridden regions.

Month by month since last November Ethiopia and Eritrea have inched closer to war, each deploying more troops almost face-to-face across their common border, supporting opposition forces in the other country, and offering sanctuary to rival proxy forces in Somalia.

After five years of Ethiopia's refusal to accept physical border demarcation, the internationally recognized Eritrea-Ethiopia Border Commission (EEBC) said, "enough."It folded its tents last November and issued its final report, a set of map coordinates that designated the exact border between the two countries, a so-called "virtual" demarcation.

Not to be outdone in dangerous decisions, Eritrea essentially expelled the United Nations peacekeeping force that had physically occupied a buffer "Temporary Security Zone" (TSZ) along the border since 2000. Both sides now have reinforced their forces on the border with heavy weapons. Eritrea pushed its forces right through the TSZ to the border, arguing it was simply moving its troops onto its legal territory, as blessed by the EEBC.

The commission had been set up as part of the 2000 Algiers peace agreement. Both countries promised to accept its subsequent rulings as "final and binding". Eritrea quickly accepted the virtual demarcation because it thought it fared well in the arbitration. Ethiopia only grudgingly accepted the arbitration, but balked at the physical marking along the border.

Now the UN has issued a blistering criticism of Eritrea for shutting off fuel from its peacekeeping force, grounding even emergency helicopters. Its actions essentially expelled the force.

Meles and Isaias, brothers in battle against the dictatorship of former Ethiopian leader Mengistu Haile Mariam in the late 1980's, seemed reasonably amicable in the years after Ethiopia recognized Eritrea's independence in 1993, accepting a land-locked status in the process. Since 1998, however, they have more closely resembled Cain and Abel, and their countries have suffered.

United States diplomats helped facilitate the Algiers Accord in 2000, and promised to support the EEBC. But the administration of President George W. Bush has been largely absent during key moments since the EEBC issued its 2002 decision, and has been mimicked by the rest of the international community, including the Security Council. Since then, few incentives were offered for compliance, and failures to abide by commitments were not followed up by sanctions.

The Bush administration has been reluctant to put pressure on Ethiopia because it considers it a regional security ally and an important player in its counterterrorism policies.  The most visible example of that policy is Ethiopia's ongoing intervention in Somalia, which has come not only with U.S. support, but perhaps by U.S. design.

The rivalry between the two nations has destabilized both countries. There are also allegations that Meles and Isaias use the threat of war to justify cracking down on political freedoms, which has created a quasi-police state in Eritrea.

Ethiopian officials told our delegation they would respect the border after normal relations were established with Eritrea. Eritrean officials said the reverse – once Ethiopia recognizes the border and Eritrean sovereignty over disputed land, normal relations will follow, including agreements on access to ports and cross-border development.

The international community must not allow events to take their dangerous course. A peace rescue package is needed before war breaks out. It must pour water on the current fuel for combat by separating the military forces, end border uncertainty and deal with underlying issues between the two countries.

• The border line delineated by the EEBC in November should form the basis of a physical border between the countries, and the Security Council should say so.
• Eritrea needs to move heavy weapons and armed encampments out of the TSZ. Ethiopia, which says it accepts the EEBC line, must remove its military forces from all land awarded to Eritrea by the EEBC.   
• UNMEE should be given full monitoring authority on both sides of the border, and report any errant troop movements.
• The physical border demarcation should begin immediately in the undisputed areas, and for those areas still in question, the countries should enter into direct talks under the supervision of a UN-authorized mediator. The Security Council should impose a fixed time-table of 90 days.
• Parallel with progressive border demarcation, mediated-talks need to be undertaken on all normalization issues—from port use to diplomatic and economic exchange to confidence-building.
• The international community needs to prepare a major cross border economic development plan to instil confidence on both sides that normalization is imminent. As soon as the physical demarcation takes place, the plan takes effect.

History can be cruel if its lessons are ignored. Ethiopia and Eritrea and its international partners are close to learning that lesson once more.

Mark Schneider is senior vice president of the International Crisis Group