The U.S. ambassador to the United Nations warned Tuesday that Washington could halt its support to humanitarian agencies operating in Houthi-controlled northern Yemen as early as March, if the Iranian-backed rebels do not stop undermining relief distribution. “The United States is also extremely concerned by mounting Houthi interference with the work of aid partners in northern Yemen, which limits the ability of the U.N. and other humanitarian organizations to deliver assistance to the most vulnerable Yemenis,” U.S. Ambassador Kelly Craft told a U.N. Security Council meeting about Yemen. Nearly 80 percent of Yemen’s population – or 24 million people – receive some form of humanitarian assistance or protection. Craft condemned actions by the rebel group, including extorting money from humanitarian groups through a 2% levy on aid projects and interference in who receives aid in areas under the group’s control. “In light of these entirely avoidable circumstances, donors are faced with the difficult dilemma of how to continue delivering aid while remaining responsive to taxpayers,” said Craft. “We may be forced to consider suspending or reducing our assistance in northern Yemen as early as March unless undue Houthi interference ceases immediately and access to vulnerable populations improves.” She called on the Houthis to take steps in line with the humanitarian principles of humanity, neutrality, impartiality and independence, and called for lifting access restrictions and removing levies on aid projects. “To the Houthis, we repeat our appeal from last month: all Yemenis in need deserve life-saving assistance,” she said. “Do not make it impossible for us to continue providing aid in the areas you control. The conditions for doing so are clear.” All council members called for a de-escalation of hostilities. A decrease in airstrikes and fighting that had seen a significant drop in civilian casualties during 2019, ended in mid-January as hostilities intensified. “Both sides have announced expansive military goals and exchanged fierce rhetoric,” U.N. Yemen envoy Martin Griffiths told council members via a video link from Geneva. “Frontlines which had been quiet for several months have been drawn into the escalation and reports of airstrikes and cross-border aerial attacks have increased considerably.” U.N. humanitarian chief Mark Lowcock told the council that the renewed fighting has displaced 35,000 people from the affected areas in just the past month. Next month, the war in Yemen will enter its sixth year. Saudi Arabia, which supports the Yemeni government, began bombing the Iranian-backed Houthi rebels in March 2015. Since then, thousands of Yemenis have been killed, mostly due to coalition airstrikes.