The Trump administration on Friday cut off tens of millions of dollars for health care programs and other aid in Yemen, rejecting pleas by humanitarian groups and some members of Congress to delay the decision as the coronavirus spreads across the Middle East.

American officials said the move was a necessary response to longstanding interference by Houthi rebels who control the northern part of Yemen. They have been fighting a civil war for the past five years and have imposed harsh restrictions on organizations trying to deliver aid. The fighting has killed thousands of civilians, and millions more face starvation in what the United Nations has labeled the world’s worst humanitarian crisis.

But as a pandemic looms, the American decision created major funding gaps for dozens of programs run by the United Nations and private aid groups, including efforts to supply the Yemenis with hand soap and medicine and to staff clinics with health care workers, humanitarian officials said.

Citing conditions that have already made Yemen a breeding ground for disease, the officials said they feared that populations weakened by hunger and packed into refugee camps would be further decimated by the coronavirus.

“This is the country that has already experienced the two biggest cholera outbreaks in recent history,” said Scott Paul, head of humanitarian policy at Oxfam America. “With the way things are now, to just take a wait-and-see attitude borders on reckless.”

No coronavirus cases have been confirmed in Yemen, but public health experts noted that large swaths of the country are without basic health care, making them difficult to surveil.

Officials with the United States Agency for International Development said the decision to halt funding, reported earlier by The Washington Post, included exceptions for “critical, lifesaving activities, including treatment of malnutrition as well as water, sanitation and hygiene programs aimed at keeping people healthy and staving off disease.”

But humanitarian officials said the agency’s exceptions did not provide for continued funding of basic health care programs, which are heavily reliant on foreign aid, and did not seem to take into account what might occur when the coronavirus begins to spread.

The United States was not alone in threatening to pull back on aid programs if the Houthis did not change their ways. The rebels tried to place a 2 percent tax on all incoming assistance and dictate who could receive aid, raising concerns that they were diverting it to fighters instead of civilians.

Earlier this year, the United States and other countries gave the rebels an ultimatum to meet benchmarks or risk losing some assistance. But only the United States, one of the biggest donors, threatened to halt all funding in Houthi-controlled areas if the rebels failed to meet more than a dozen requirements by Friday, humanitarian officials said.

In the weeks since, the rebels made some progress, the officials said. Then the threat of the coronavirus came into sharper focus, prompting aid groups and others to plead with the American aid agency to wait another month before cutting off funding.

On Thursday, Democratic lawmakers, including Representatives Eliot Engel of New York, the chairman of the House Foreign Affairs Committee, and Adam Smith of Washington, chairman of the Armed Services Committee, sent a letter to Secretary of State Mike Pompeo and the Agency for International Development administrator, Mark Green, expressing concern about the pending decision.

“A suspension of assistance during a pandemic would risk the health response in a country in which 50 percent of its health care is offline due to fighting,” the lawmakers wrote. “Given the U.S. is among the largest humanitarian donors to Yemen, abruptly ceasing aid would exacerbate an already tragic humanitarian crisis.”

Still, the American aid officials decided to halt the funding, cutting off about $70 million in assistance destined for the northern part of Yemen. The south, which is less populous, still receives aid dollars, the officials said.

A spokesman for the U.S. Agency for International Development said the Houthis were to blame for interruptions of aid to Yemeni people.

“We are extremely concerned that the Houthis have already caused millions of people to lose access to lifesaving humanitarian assistance and worsened the effects of Yemen’s humanitarian crisis,” the spokesman said. “The coronavirus pandemic demonstrates now more than ever the need for our partners in Yemen to be able to deliver aid to those who need it most without interference or delay.”

The United States gave more than $700 million in aid to the United Nations and other organizations working in Yemen last year, with a significant portion going to programs in the Houthi-controlled northern part of the country.