Should the Trump administration formally designate Yemen’s Houthi rebels as a terrorist organization, aid groups say it would greatly undermine their ability to deliver life-saving assistance to millions of civilians and worsen what the United Nations calls the world’s worst humanitarian catastrophe.

In an effort to financially squeeze the Houthi group and pressure its regional backer, Iran, the State Department is considering naming the entire Houthi movement a foreign terrorist organization, as reported by Foreign Policy earlier this week. Saudi Arabia has lobbied hard for the terrorism designation, which would criminalize material support for the Houthis, trigger an asset freeze and impose a travel ban to the United States. The Trump administration might instead designate individual Houthi leaders as specially designated global terrorists, said a source familiar with the matter, in a mostly symbolic action that carries similar financial sanctions.

The Iran-aligned group has waged a nearly six-year war in Yemen against a Saudi-led military coalition that intervened in early 2015 to restore the internationally recognized government. The fighting killed more than 100,000 people, devastated Yemen’s health infrastructure and pushed the impoverished country to the brink of famine. 

Relief organizations operating in Yemen warn that slapping a terror label on the Houthis could hamper aid work in a country where an estimated 80% of the population — more than 24 million people — is reliant on humanitarian assistance to survive, a majority of whom live in Houthi-controlled areas in the country’s mountainous north.