The UN needs $US200 million to keep its food distribution in Yemen at current levels.
The UN will be forced to scale back already limited food distribution in Yemen by August because of severe funding shortages, a senior official says.
About 14 million people, or roughly half the country's population, suffer from food insecurity at "crisis" or "emergency" levels, said George Khoury, head of the UN Office for the Co-ordination of Humanitarian Affairs in Yemen.
Emergency level is just one step before famine on the UN's food insecurity scale.
The World Food Program currently reaches about 3.5 million people in Yemen every month.
Khoury said in an interview on Wednesday that without more funding, "we don't have enough money to feed even these people".
The WFP would need about $US200 million ($A268 million) to keep its food distribution at current levels in the coming months, he said.
UN agencies requested $US1.8 billion in overall aid for Yemen in 2016, but only 20 per cent of that money has arrived, Khoury said.
The Yemen conflict pits Shi'ite Houthi rebels and allied troops loyal to a former president against Yemen's internationally recognised government.
The Houthis seized the capital, Sanaa, in September 2014, forcing President Abed Rabbo Mansour Hadi to flee, first to the southern port city of Aden and later to Saudi Arabia.