The effort expended by two of Africa's poorest countries on this fruitless border war is enormous. An hour-long flight in an Ethiopian army helicopter, feet above tree level, reveals mile after mile of deserted trenches, with no signs of life and little sign of battle. Behind the lines, years of drought have left millions facing starvation.

But Ethiopia says that recapturing lost territory comes first. "Sovereignty is not a luxury for the rich alone," said Meles Zenawi, the prime minister, who last month appealed for 800,000 tons of emergency food aid.

Boxes of ammunition, heavy machine guns, rocket-propelled grenades and empty Coca-Cola cases litter the small military camps which the Eritrean army clearly evacuated in a hurry.

Along the roadside the advancing Ethiopians have tied red ribbons to the trees as a warning of land mines. tens of thousands have been planted since the war broke out. Ethiopian T-55 tanks are careful not to stray from the dust track that passes for a road.

Ethiopian troops, on leave from the front, mill around the town of Tokombia, which they captured on Saturday and have been looting ever since. The thousands of empty beer bottles are perhaps the clearest sign that the army feels it is on the verge of victory.

Colonel Ghebre Kidan of the Ethiopian army said the capture of Barentu had cut the Eritrean supply lines and had effectively ended the war on the western front.

But his aim of "ensuring that this invading army is never capable of occupying our territory again" seems a more distant objective.

There remain the central Zalambessa front and the eastern Bure front, both of which have seen heavy fighting in the past few days.

The offensive began on Friday, just days after the US ambassador to the UN, Richard Holbrooke, completed the latest of a series of efforts by African and western leaders and diplomats to end the conflict peacefully.

In a show of strength and a test of political will, the Eritrean forces pushed into Ethiopia in May 1998 as relations between the two former allies deteriorated because of economic differences.

Eritrea did not plan for the disaster that has since unfolded in a bitter conflict which has divided families and friends and cost both countries hundreds of millions of pounds, tens of thousands of lives, and a significant loss of standing in the international community.

Ethiopian officials, not known for their candour, are now openly giddy with their troops' success in the past few days.

They now control large swaths of southern Eritrea, and hope that this offensive will put an end to the war, put Eritrea in its place, and let their countries restart their much needed development.

The international community was swift to condemn the latest outbreak of fighting, calling it a "senseless war", and gave both parties 72 hours to end hostilities or face sanctions.

That call went unheeded and the United Nations, blighted by a string of recent peacekeeping failures in Africa, has now imposed a one-year arms embargo on both countries.

But that may be too late. Both sides have embarked on costly rearmament programmes since the war began, and an Ethiopian spokesman said yesterday: "We are now getting all the weapons we need from the defeated Eritrean forces.

In Ethiopian held Eritrea, an Eritrean MiG-29 screamed through the sound barrier, firing flares to distract heat-seeking missiles before dropping its load close to an Ethiopian artillery battery and a small group of western journalists.

Ethiopian sources said later that the plane had been shot down soon after releasing its bombs.

But for now thousands of Eritrean prisoners of war like Michaele Stefanos must await the outcome of the war before they know their fate.

When the fighting began two years ago Mr Stefanos was a student in the Ethiopian capital, Addis Ababa. In March he was deported because he is Eritrean, and when he arrived back in Eritrea he was conscripted into the army, because he is young and fit.

He said that he was glad to have been captured, that he had never wanted to fight, and that he still did not understand what thousands of young men and women were dying for. "From now on I never want to see another bullet again."