SOME 50 TO 100 children are already dying daily in northern Ethiopia as the result of a famine that could become one of the worst in African history, Post correspondent Jay Ross reported from Addis Ababa yesterday. This staggering prospect is the product of factors familiar in Ethiopia and many other states in Africa and elsewhere in the Third World. The margin is very narrow in most of those countries. Things must go well for them just to subsist. If even one big thing goes wrong, the price is heavy. In Ethiopia, on top of the usual suspects--poverty, underdevelopment, drought--local wars and the policies of the Ethiopian government have combined to put the country on the brink of an immense catastrophe.

In the wars going on in Eritrea and Tigray provinces, food is a weapon of war. This is especially true of the Ethiopian regime, whose efforts to pry local populations out of their support for rebellion often seem to center on depriving them of food and the means of a normal existence, such as it is.

In the past, Ethiopia turned first to the United States for emergency food aid. But the repressive Marxist regime now in power has cast its lot with the Soviet Union and its clients, Cuba and Libya. These friends of Ethiopia choose to leave it pretty much on its own when it comes to food. Col. Mengistu Haile Mariam, the country's leader, cannot bring himself to interrupt even briefly his political attacks on the United States and to ask for relief for his suffering people. This task has been delegated to relief officials in his government or assigned to the international relief agencies.

The United States has done relatively little to help Ethiopia meet its growing crisis. Essentially taking the view that the Ethiopian government has made its own choices, the Reagan administration suggests it is up to that government to exhaust all other sources of food aid, European and international, before making further requests of Washington.

We can understand the reason for the United States' giving first call on its available resources to friendlier governments. And there is an irony in the United States' being expected to show more compassion for starving Ethiopians than their own government shows. But it's not as if we were running out of the resources with which to help those desolate people. And surely there is something beyond irony at stake here: there is something desperately wrong when the United States does less than it could to help keep a dying population alive. This country could be especially useful if it were to provide trucks or aircraft to distribute supplies inside Ethiopia, and it could certainly send more food. Whatever the politics, the moral choice is not complicated at all--this country must help the starving Ethiopians and help them now.