Without more aid money, the World Food Programme fears it will not be able to help all eight million people going hungry in Niger.
Relief agencies in Niger are struggling to tackle a food crisis in the west African country after poor rains last year left millions short of food.
"With the limited resources, it will be very difficult, even impossible, to meet the initial target (of 7.9 million people) unless donors come forward as quickly as possible," a spokesman said.
The agency says it needs an extra £56million ($88m) to feed eight million people until the end of the year.
It is so desperate for cash, the agency has resorted to feeding children under two first, because they are most at risk from potentially life-threatening malnutrition.
"With the limited resources, we have made the difficult decision to concentrate on these children and their families in the most affected regions," the WFP spokesman told Reuters news service.
About 17 per cent of Niger's under five-year olds are not getting the vitamins and nutrients they need – way more than the 15 per cent needed to make the situation an official crisis − and the rate is higher still among under-twos in some parts of the country.
The agency’s decision to prioritise feeding under two year olds means that, the rest of Niger’s 60 per cent of people going hungry will have to depend on the "woefully under-resourced" government and other aid groups.
"No humanitarian agency should be forced into such an impossible position, especially one backed by the entire international community," said Oxfam’s Raphael Sindaye.
"This is an appalling situation. We have known about this crisis for months and yet more than a million people in Niger will continue to starve over the coming weeks and perhaps months," she told the news service.
It comes just as it was announced that aid workers on the hunger relief effort have been pulled out of some parts of the country because of security threats, plunging the situation into further crisis.
Workers are being pulled out of Maradi, in the south, and Zinder, in the east, both areas at the centre of the food shortage.
"I can confirm that the World Food Programme has told its staff based in Maradi and Zinder to evacuate and return to Niamey due to security reasons," Vigno Hounkanli, a WFP spokesperson said yesterday (Monday).
Two other aid workers said all United Nations agencies and charities were pulling Western staff out of the region for fear of kidnappings by groups linked to al Qaeda. One said it would have a ‘massive impact’ because the workers are treating thousands of malnourished children every week.