A Save the Children flight will arrive tonight in Niamey, the capital. The World Food Programme will be airlifting in generators, tents and pick-up trucks by the end of the week.
The plight of the starving children has caught the attention of the world, because of the heart-rending images on television but the race to bring aid to the severely malnourished children has only just begun.
Dr Mego Terzian, a Médecins sans Frontières co-ordinator in Maradi, the region about 400 miles east of Niamey which is suffering from poor rainfall and a locust infestation, said: "Things are moving, but very slowly at the moment."
Toby Porter, the director of emergencies for Save The Children, said: "It's not a famine. These kids are starving to death because they are poor." He said the "hidden emergency" had been caused by the chain of events occurring in one of the world's most impoverished countries. The lack of rain, followed by poor harvest and a steep rise in the price of millet had pushed more than one third of the population over the edge.
Mr Porter said: "The Make Poverty History campaign said a child in Africa dies every three seconds. This is what it looks like."
The UN put out urgent appeals to raise funds for 2.5 million people in Niger 10 months ago but received no money until children began starving to death.
But while aid agencies and governments have rushed food to Niger, its neighbouring countries are still in need of help. The UN is warning that the food shortages will spread to other countries in the Sahel desert, such as Mali, Burkina Faso and Mauritania.
Last year, West Africa fell victim to the largest invasion of locusts in 20 years. The insects, combined with the poor rainfall and the desertification of once-fertile agricultural lands, helped destroy the harvests in all the countries of the Sahel.
In Mauritania, the country hardest hit by the insects, the entire harvest has been wiped out. The cereals, pulses and vegetables that are a sole source of food for 750,000 people, or a quarter of the population, have been destroyed.
In Mali, last year's droughts and locusts had reduced agricultural output by 42 per cent. The UN estimates 1.1 million people will need food aid, and warned 5,000 children in the north of the country are already close to death.
The World Food Programme wants to reach 450,000 people who have been hardest hit by the problems but, because of funding difficulties, it has so far been able to reach only about 86,500.
Meanwhile, in Burkina Faso, 500,000 people need help to get food.
The International Federation of Red Cross and Red Crescent societies launched an emergency appeal last week to raise $14m (£8m) for the region, and echoed warnings from Médecins sans Frontières that eight million people in the region faced famine.
The societies said: "Compared with Niger, Mali, Burkina Faso and Mauritania are not yet as affected but are also reaching an alarming situation."
The food crisis in West Africa has raised questions about how soon the international community should intervene to prevent such problems in the developing world. The UN's Food and Agriculture Organisation flew in planes to spray the locust-infested areas in West Africa last year with pesticides.
But a lack of funding meant they could not reach all the locusts' breeding grounds in time.
At a meeting in Senegal last year, UN officials warned the locust problem could get worse. They predicted the swarms would expand in Morocco, Algeria, Tunisia and Libya and then move back south.
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