The United Nations issued an ultimatum Friday - if donors fail to pour more money into Africa and Yemen then aid workers might have to choose which of the starving millions live or die.
"We are going to have to make life challenging decisions as to who will receive food and who will not," said David Beasley, head of World Food Programme.
"This is not a decision that we look forward to making, but that is the reality, the graveness of the situation," Beasley told a conference at the UN Food and Agriculture Organisation.
More than 30 million people need food assistance in Yemen, South Sudan, Nigeria and Somalia due to conflict and drought.
Speaking by video link from Geneva, Beasley said UN agencies currently only had enough money to help 8.4 million of them.
Wars in Yemen, northeastern Nigeria and South Sudan have devastated households and driven up prices, while a drought in east Africa has ruined the agricultural economy.
"If we don't act urgently in the next weeks we will have the same famine probably in Somalia," FAO director-general Jose Graziano da Silva told the conference.