The World Food Program (WFP) started on Thursday a partial suspension of its operations in areas in Yemen that are controlled by the Iran-backed Houthi militias.
The UN agency said it suspended its operations in the capital, Sanaa, which has been under Houthi control since 2014. The suspension would affect 850,000 people, it said in a statement.
The move came less than a week after the head of the WFP accused the Houthis of diverting food aid.
"The decision was taken as a last resort after lengthy negotiations stalled on an agreement to introduce controls to prevent the diversion of food away from some of the most vulnerable people in Yemen," the agency said.
The WFP said it failed to reach an agreement with the Houthis on introducing "a biometric registration system that would prevent diversion and protect the Yemeni families we serve, ensuring food reaches those who need it most."
The agency said it has repeatedly appealed to the militias for "space and freedom to operate ... impartiality" and with operational independence.
WFP said it would maintain nutrition programs for malnourished children, and pregnant and nursing mothers throughout the period of suspension.
On Monday, David Beasley, executive director of the World Food Program, told the UN Security Council that his agency has insisted on — and the Houthis finally agreed to — registration and biometric identification of beneficiaries and monitoring in December and January, but the WFP has faced roadblocks ever since in implementing the agreements.
"If we do not receive these assurances, then we will begin a phased suspension of food assistance, most likely toward the end of this week," he said.
The Associated Press reported December 31 that armed factions on both sides of the conflict were stealing much-needed food aid, diverting it to their fighters or reselling it for profit.
Some groups are blocking deliveries to communities they view as their enemies, the AP found. WFP confirmed the report.
On January 1, the Houthis said they were "surprised" by the WFP's accusations and accused the food agency of taking sides in the war.
Beasley told the council Monday that the diversions were mainly in Houthi areas. When there are reports in government-controlled areas, he said, "we receive cooperation to address issues."
The biometric system - using iris scanning, fingerprints or facial recognition - is already used in areas controlled by the legitimate government.
