The UN's World Food Programme said it had been "compelled to pause" distribution of food to millions of people living in Houthi-controlled areas of Yemen.
The WFP said it had failed to reach an agreement with the de facto authorities in the capital Sanaa, despite talks throughout the year to scale down operations.
“This difficult decision, made in consultation with donors, comes after nearly a year of negotiations during which no agreement was reached, to reduce the number of people served from 9.5 million to 6.5 million,” it said in a statement.
Food stocks in areas under Houthi control “are now almost completely depleted and resuming food assistance, even with an immediate agreement, could take up to as long as four months due to the disruption of the supply chain", the WFP said.
UN spokesman Stephane Dujarric said the WFP had tried unsuccessfully “to establish a system that is safe and accountable for the aid going through” to rebel-held areas.
The war in Yemen began when the Houthis seized Sanaa in 2014. More than 150,000 people have since been killed by the violence and three million displaced.
The WFP said it would continue its nutrition and school-feeding projects, to limit the impact of the pause in food distribution.
In government-controlled areas of Yemen, the WFP said general distribution would continue “with a heightened focus on the most vulnerable families".
“Similar prioritisation is taking place in nearly half of WFP’s operations around the world as the agency navigates the challenging financial landscape that the entire humanitarian sector is facing,” it added.
