The window of opportunity to save people from hunger in Africa's Sahel region is narrowing by the day.
In a joint statement, the two agency chiefs are appealing to the international community to act on behalf of millions of vulnerable people.
WFP chief Ertharin Cousin says the food crisis in Niger has been compounded by the conflict in Mali.
"You have refugees coming into Niger. We've seen about, 35,000 refugees from Mali into Niger, so the food crisis is even more complicated this year than it was in 2005 and 2010. So this is one where the international community cannot, must not, ignore."
WFP has scaled up its food operations in Niger, while UNHCR is helping 160,000 people who have fled fighting in Mali to neighbouring countries, including Niger.