United Nations food chief David Beasley warned on Monday that a phased-suspension of food assistance in Yemen was likely to begin later this week over a diversion of aid and lack of independence in Houthi-controlled areas.
Beasley, executive director of the World Food Programme (WFP), called on the Houthis to "simply let us do our job."
"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. If and when we do initiate suspension we will continue our nutrition program for malnourished children, pregnant women and new mothers," he told the UN Security Council.
Beasley said WFP had been unable to implement agreements with the Houthis on the registration of people in need and the rollout of a biometric system - using iris scanning, fingerprints or facial recognition - to support aid delivery.
"We are now assisting feeding over 10 million people per month but as the head of the World Food Programme I cannot assure you that all the assistance is going to those who need it most," Beasley said.
"Why? Because we are not allowed to operate independently and because aid is being diverted for profit and or other purposes," he told the 15-member council.
The Houthis did not immediately respond to a request for comment on Beasley's remarks. However, earlier this month Mohammed Ali al-Houthi, head of the Houthis' Supreme Revolutionary Committee, told Reuters the WFP insisted on controlling the biometric data in violation of Yemeni law.
A Saudi-led coalition intervened in Yemen in 2015 to try to restore the internationally recognized government that was ousted from power in the capital, Sanaa, by the Houthis in 2014.
The conflict is widely seen in the region as a proxy war between Saudi Arabia and Iran. The Houthis deny being puppets of Iran and say their revolution is against corruption.
Beasley said that aid diversion was not limited to just Houthi-controlled areas, but "when we face challenges in areas controlled by the government, we have received cooperation to address the issues."