The United Nations made an 11th-hour appeal to the Trump administration this week about the likelihood of a humanitarian disaster in Yemen ahead of an expected decision to name Houthi rebels there as a terrorist organization, as U.S. officials prepared to potentially halt a $700 million aid program for the country.

In a meeting with Secretary of State Mike Pompeo, David Beasley, executive director of the U.N. World Food Program, expressed his “grave concerns” about the impact of a decision to designate the Iranian-backed rebel group as a foreign terrorist organization, which individuals familiar with the matter say Pompeo could finalize as early as this week.

“I’ve got to have as much cover and flexibility as I can . . . in this complex working environment, where the Houthis control access to almost every single piece of territory,” Beasley said in an interview after meeting with Pompeo on Tuesday.

In recent weeks, officials from the United Nations and aid groups have issued increasingly urgent warnings, saying a designation could dramatically worsen already dire conditions in Yemen by reducing the amount of lifesaving aid and commercial imports moving into the country.

Five years of war between the Houthis, who function as Yemen’s government in vast areas of the country, and a Saudi-backed military coalition have helped stoke disease, hunger and suffering, contributing to what has become the world’s worst humanitarian crisis.

Now, the deteriorating situation among millions of Yemenis appears to be careening toward a collision with the Trump administration’s desire to advance its hawkish Iran policy in its final days in office. In addition to unveiling new sanctions on Tehran, Pompeo is expected to announce a decision on the terrorist designation for the Houthis, along with potential lesser steps to sanction the group, officials familiar with the discussions said, speaking on the condition of anonymity to describe the internal conversations.

If finalized, the move would subject individuals or groups who interact with the Houthis to financial sanctions and possible criminal prosecution unless they secure administrative exceptions from the U.S. government.

Officials said it was not yet clear whether the administration would promptly issue waivers that would allow U.S. government employees, and the aid groups they fund, to continue their work. If they aren’t in place in time, all U.S. and U.S.-funded activities will be forced to halt immediately. Officials have already prepared “cease and desist” letters in case that happens.

A State Department spokesman declined to discuss potential designations.

A full halt to U.S. aid activity, which has already been cut back this year, could have a devastating impact for Yemen. New U.N. data, which was obtained by The Washington Post ahead of its release, showed that hunger is worsening in Yemen, as pockets of Yemenis are experiencing famine-like conditions for the first time in several years. The number of people who fall in that category is expected to grow to as many as 47,000 in the next six months.

Beasley, a former South Carolina governor, said Pompeo voiced concern about the circumstances of ordinary Yemenis and also about the activities of the Houthis.

The U.N. official said he expressed to Pompeo the importance of securing waivers that would allow aid groups to continue their work. “I told him it’s a bad situation, and it’s getting worse,” he said.

Aid workers say a terrorist designation for the Houthis could have a greater impact in disrupting aid and even commercial trade flows of food and medicine into Yemen. That’s because unlike most other groups designated as terrorist organizations, the Houthis control an area that is home to 70 percent of the population, including the capital and major sea and air ports.

Current and former officials have warned the move could have the unintended effect of deterring commercial shipping, insurance and trade companies from working in Yemen for fear of running afoul of U.S. law. Initial legal waivers sought by American officials would not extend to non-U.S.-funded aid work, leaving those groups in legal limbo for at least some period.

Despite attempts to establish carve-outs, such designations have resulted in dramatic reductions to aid in the past, as occurred with deadly effect in Somalia more than a decade ago. Beasley said the situation in Yemen is far more complex than Somalia because Yemen is almost entirely dependent on imported food and because the Houthis control major infrastructure, a point he made to Pompeo.

The United States has already this year cut back much of its aid, which totaled more than $700 million in 2019, to Houthi-controlled areas of Yemen due to rebel restrictions on humanitarian work. As a result of reduced funding from the United States and other nations, the United Nations has already reduced its food rations to millions of Yemenis.

Senior officials from the U.N. Children’s Fund (UNICEF) have also expressed concern about the designation in recent conversations with State Department leaders. More than 12 million Yemeni children are in need of humanitarian aid.

“UNICEF would be deeply concerned about any decisions that could compromise the safety of our teams and their efforts to assist vulnerable children and families,” Christopher Tidey, a spokesman with the agency, said in an email.

American officials say the Houthis have received military support from Iran, including missiles and drones, which they have used to attack Yemen’s neighbor to the north, U.S. ally Saudi Arabia.

Saudi Arabia, meanwhile, has been blamed for thousands of civilian deaths in Yemen in its air war against the Houthis. The United States, which used to conduct in-air refueling for Saudi jets as part of the Yemen operation, has scaled back its support for the coalition.