The Trump administration plans to move forward with a major reduction of humanitarian assistance to Yemen effective Friday in response to restrictions imposed on aid by Iranian-linked Houthi rebels, U.S. officials and relief workers said.

U.S. officials, who spoke on the condition of anonymity to discuss a decision that has not been announced publicly, say the move is intended to prompt the rebels to lift measures in areas of Yemen they control that have made it difficult for aid groups to operate.

But aid officials warn the cut could prove disastrous ahead of what many fear will be a crippling coronavirus outbreak in a country that is already the scene of the world’s worst humanitarian crisis.

“There is no question. We are running out of money,” Lise Grande, the U.N. humanitarian coordinator for Yemen, said in an email from Sanaa. “Many of the operations which keep people alive will close next month if funding doesn’t come very soon. Already health, protection and water programs are being scaled back.”

The Houthi rebels, who have controlled much of Yemen, are in the fifth year of a punishing conflict with a military coalition led by Saudi Arabia. The United States provided aerial refueling to coalition jets until 2018 and continues to share certain intelligence related to Yemen.

The U.S. decision caps weeks of speculation about a possible cutoff for Yemen and behind-the-scenes efforts by U.N. officials, aid workers and diplomats to pressure the Houthis to loosen rules that have impaired aid delivery and, humanitarian officials say, made it impossible to ensure that assistance isn’t diverted for military or other purposes.

While the Houthi government rolled back some of the measures — including a proposed 2 percent tax on all aid — in response to an international outcry last month, other restrictions, including delays in granting travel permits, remain in place, aid groups say.

Now, the U.S. Agency for International Development (USAID) says it has made the “difficult decision” to cut assistance, with exceptions for certain “lifesaving” aid.

A USAID spokesman said the reduction would occur in Houthi-controlled areas because the rebels had “failed to demonstrate sufficient progress towards ending unacceptable interference” in aid operations.

“We continue to demand that all assistance be provided in accordance with humanitarian principles to ensure it is reaching those who need it most,” he said. Aid to areas not controlled by the Houthis would continue, he said.

The spokesman said operations would be evaluated as the covid-19 situation evolves. According to USAID, at least $73 million out of a total of $85 million in aid delivered via nongovernmental groups in the Houthi-controlled north will be suspended immediately. The agency said some aid to the United Nations, including support for U.N. flights and coordinating activities, would continue, but it was not immediately clear what would happen to food assistance channeled through the United Nations. Last year, the United States provided more than $740 million for humanitarian operations in all of Yemen, a fifth of all humanitarian funding for the country, aid officials said.

“Everybody’s ripped up about this. This goes against the grain of people’s emotions,” a U.S. official said. “While the stakes are very high and we definitely don’t want to cut off lifesaving assistance, the pressure needs to continue until they fall in line.”

Officials who have been in discussions with USAID say the exceptions are expected to permit only scant amounts of aid to continue, including inpatient treatment for malnutrition and medical care related to a major cholera outbreak.

If confirmed, that would mean much of the support to the country’s battered health sector would end. Also affected would be assistance to camps where people displaced by fighting live in crowded conditions; support to water and sanitation networks; and education about health and hygiene, which is seen as particularly critical at this time.

Though no confirmed covid-19 cases have been reported in Yemen, the country has limited testing capacity and a health system severely degraded by poverty and war.

“The thing that’s pretty amazing, not in a good way, is that as covid has become a pandemic and humanitarian organizations brace for an urgent ramp-up to stop its spread, the suspension is proceeding like we’re doing business as usual,” said Scott Paul, humanitarian policy lead for Oxfam America. His organization is calling for a delay of at least a month in implementing any aid reduction.

Aid officials say large U.S. cuts could mean that more than 5 million people could go without emergency health service; millions could go without food. Already this week, the U.N. World Food Program said it would reduce food rations by half because of funding shortfalls and Houthi restrictions.

In a letter Thursday to Secretary of State Mike Pompeo and USAID Administrator Mark Green, four Democratic lawmakers called the Houthi restrictions unacceptable but urged the administration to hold off on a large-scale reduction in aid.

“Given the U.S. is among the largest humanitarian donors to Yemen, abruptly ceasing aid would exacerbate an already tragic humanitarian crisis,” the lawmakers, including the chairmen of the House Armed Services Committee and House Foreign Affairs Committee, wrote.

A humanitarian official in Yemen said people already were starving. “Families all across Yemen depend on the generosity of the American people to survive. Now they are being punished and now they will die,” the official said.

Christine Cool, a project coordinator for the U.N. Office for the Coordination of Humanitarian Affairs, said the World Health Organization continued to do what it could to help Yemen prepare for a coronavirus outbreak, establishing hotlines, assisting hospitals establish isolation units and facilitating the delivery of supplies.

But the situation is extremely fragile. “An introduction of covid in Yemen would be catastrophic for the country, given the powder keg of exacerbating factors,” she said.

The U.S. official said the decision was not driven by the Trump administration’s “maximum pressure” campaign on Iran, which has included sanctions and measures to crack down on Iranian-backed proxy groups. While the Houthis are not thought to have as close ties to Iran as groups in Iraq, Syria and Lebanon, officials say they have received some military support from Tehran.