The Trump administration’s plan to designate Yemen’s Houthi rebel movement a foreign terrorist group, part of an 11th-hour effort to pile pressure on Iran and its allies, has left officials and aid workers scrambling to a prepare for a move critics warn could have catastrophic consequences.

Individuals familiar with the discussion said officials are racing ahead of an expected December announcement to draft exceptions that would, in theory, make it easier for U.S. and other aid agencies to continue their work without fear of breaking the law.

The administrative carve-outs would be designed to allow aid groups to continue operating in Yemen — where a long-running war has helped spawn a humanitarian crisis — without fear of sanctions or prosecution for links to a terrorist organization.

But aid groups are already expressing alarm that those measures will fail to avert a dramatic reduction in lifesaving assistance and commercial shipments of food and other items to a nation teetering on the brink of famine. They also fear the designation could sabotage hopes for a peace deal and prolong a war in which hundreds of thousands of people have died.

“If this is rushed through, we might see trade and financial flows dry up across Yemen, the diplomatic process blown up and the Houthis deciding they need to repay the favor by increasing the tempo of attacks into Saudi Arabia while turning to Iran for more support,” said Peter Salisbury, senior analyst for Yemen at the International Crisis Group.

Preparations for the announcement are part of a push by the Trump administration to cement long-delayed policy goals before Inauguration Day on Jan. 20, such as pulling troops out of Afghanistan, even as President Trump challenges the results of the Nov. 3 election.

In the administration’s waning days, officials have also introduced new measures intensifying the “maximum pressure” campaign on Iran and its allies, despite criticism that Trump’s signature policy has failed to curtail Iran’s oil trade and uranium stockpile expansion. 

On Wednesday, Secretary of State Mike Pompeo, who has touted his record on Iran as one of his principal achievements, said the United States would slap new sanctions on Iran to “preserve the safety of the region and to protect American lives.” The sanctions are expected to be rolled out on a weekly or even daily basis until President-elect Joe Biden takes office.

The Trump administration has cast the war in Yemen as another reason for its Iran campaign, though officials say the Houthis, who are formally known as Ansar Allah and come from a Shiite sect from northern Yemen, initially received only minimal support from Iran, despite claims to the contrary from Saudi officials.

But Iranian military support has increased steadily throughout the war. Nevertheless, the Houthis are seen as more independent than other proxy groups, such as Hezbollah in Lebanon.

Some officials at the State Department’s Near East bureau, the U.S. Agency for International Development and the Pentagon, fearing a designation could compound suffering and derail a halting peace process, have argued against the designation or suggested deferring a decision until after Jan. 20.

But Pompeo in recent weeks capped the internal debate by requesting new options and indicating that he would move ahead with designating the Houthis as an official terrorist group, with a tentative deadline of Dec. 1. A State Department spokesman said the United States does not preview decisions about terrorist designations, and officials said the timeline might change.

Individuals familiar with the discussions said Pompeo also indicated he planned to designate the group under a separate counterterrorism authority in tandem.

The deliberations come at a particularly grim moment for Yemen, where fighting and economic collapse have contributed to record malnutrition and disease. Earlier this year, the U.S. government suspended much of its aid to Yemen after the Houthis imposed restrictions that made it difficult to ensure the deliveries were going to intended recipients.

On Friday, U.N. Secretary General António Gutteres said that Yemen was now in imminent danger of “the worst famine the world has seen for decades.”

“In the absence of immediate action, millions of lives may be lost,” he said.

A U.S. designation would mark a triumph for Saudi Arabia, which leads a military coalition that has been battling the Houthis since 2015. The Houthis have lobbed rockets and missiles into the kingdom that Saudi officials say have killed civilians. Saudi jets, meanwhile, have repeatedly bombed civilians in Yemen.

The Trump administration has forged a close relationship with Saudi Arabia, despite its handling of the Yemen war, the killing of Washington Post contributing columnist Jamal Khashoggi and other events.

Individuals familiar with the discussion said officials are trying to put together administrative exceptions that would allow U.S. and other aid agencies to continue their work.

Jason Blazakis, who for a decade served as director of the State Department office that oversees terrorist designations, said the Treasury Department could issue a “license” that would permit Americans to conduct certain kinds of activities with the Houthis, such as aid delivery, without facing sanctions. But he said preparing those licenses could take months, potentially creating a life-threatening delay.

The State Department could also issue waivers that allow U.S. government agencies to continue their work in Yemen, similar to provisions that have been made for aid delivery in militant-controlled areas of Syria.

But experts said efforts to shelter humanitarian work from being disrupted by counterterrorism designations have failed in the past. After the Somali militant group al-Shabab was designated in 2008, nongovernmental groups and even USAID were unable to operate in large parts of the country because of the lack of a clear U.S. government statement about exemptions for such work — a fact that experts say contributed to the impact of a 2011 famine.

Experts say the situation could be even more dire in Yemen because the Houthis function as the government in much of the country, including the capital, overseeing areas where 70 percent of Yemenis live.

“It’s one thing to designate a foreign terrorist organization that does not control any territory. It’s quite another thing when that terrorist organization basically runs a country,” said Adam M. Smith, a partner at Gibson, Dunn & Crutcher who served at the Treasury Department and White House during the Obama administration.

Uncertainty about who could legally operate in Yemen after a terrorist designation would probably have a much broader impact than intended, potentially disrupting commercial shipping amid concern among global banks and insurance and shipping companies about running afoul of U.S. law.

Smith said the power of U.S. sanctions and terrorism designations rests in part on ambiguity about who might be subject to penalties for possible violations, acting as a deterrent to engagement with those groups. On the flip side, such restrictions can also have an unintended effect on activities that the government wants to support, including aid work, if they are not paired with exceptions and licenses.

“The problem is that surgical targeting of bad actors can become unsurgical very quickly,” he said.

Scott Paul, a humanitarian-policy official at Oxfam America, said that strong exceptions for humanitarian work were essential. “These will mitigate some of the harm, but this decision will still ultimately cost lives in Yemen,” he said.

Greg Ramm, vice president for humanitarian response at Save the Children, said the expected move defied the reality that aid workers face in places such as Yemen. “Our work as humanitarians is to work with the authorities in charge to get access to those in need, and anytime something like this happens, it makes it much harder,” he said.

Foreign Policy reported earlier this week that the administration planned to make the designation.

The plan has already generated opposition on Capitol Hill. On Friday, a bipartisan group of lawmakers unveiled a new war-powers resolution that would force a vote on the U.S. participation in the war in Yemen. The measure was co-sponsored by Reps. Peter A DeFazio (D-Ore.), Debbie Dingell (D-Mich.), Andy Biggs (R-Ariz.), Joaquin Castro (D-Tex.), Mark Pocan (D-Wis.), Ro Khanna (D-Calif.), Francis Rooney (R-Fla.) and Matt Gaetz (R-Fla.).

Last year, Trump vetoed a war-powers resolution related to the war in Yemen, an unusual congressional effort to tie the commander in chief’s hands indicating an increasingly tough congressional stance on Saudi Arabia. The United States has already halted most of its support to the Saudi-led coalition but continues to share intelligence and provide some logistical support.

The congressional push was prompted by concern that the designation will have a “very limited impact on the Houthis aside from restricting aid, as they don’t have foreign bank accounts or travel much abroad,” said Erik Sperling, executive director of Just Foreign Policy, which worked with the lawmakers in the legislation.

A draft of the resolution, obtained by The Washington Post, says the Saudi-led war has helped produce the “world’s largest humanitarian crisis.”

Ellen Nakashima contributed to this report.