The United Nations warned Wednesday the risk of mass starvation is rapidly rising in Yemen, Nigeria, Somalia and South Sudan. U.N. spokesperson Adrian Edwards said a preventable humanitarian catastrophe is “fast becoming an inevitability.”

Adrian Edwards: “The risk of mass deaths from starvation among populations in the Horn of Africa, in Yemen and Nigeria, is growing. This warning is in light of the drought situations that you’ve been hearing about, that are also affecting many neighboring countries, and a funding shortfall that has become so severe that an avoidable humanitarian crisis in the region, possibly worse than that in the case of the Horn of Africa of 2011, is fast becoming an inevitability.”

Earlier this year, the U.N. appealed for $4.4 billion to prevent famine, but has received only about one-fifth of those funds. The U.N. warning came as a group of 55 U.S. lawmakers wrote to Donald Trump warning the president needs congressional approval if he seeks to expand U.S. support for the Saudi-led bombing campaign and blockade of Yemen.