WASHINGTON — The Trump administration has lauded itself as leading the world in confronting the coronavirus. But it has so far failed to spend more than 75 percent of the American humanitarian aid that Congress provided three months ago to help overseas victims of the virus.

In two spending bills in March, lawmakers approved $ 1.59 billion in pandemic assistance to be sent abroad through the State Department and the United States Agency for International Development.

As of last week, $ 386 million had been released to nations in need, according to a government official familiar with the spending totals that the State Department has reported to Congress for both agencies. That money was delivered through private relief groups and large multinational organizations, including United Nations agencies, that provide health and economic stability funding and humanitarian assistance around the globe.

Of that, only a meager $ 11.5 million in international disaster aid had been delivered to private relief groups, even though those funds are specifically meant to be rushed to distress zones.

The totals reflected spending on the global coronavirus response as of June 3 by the State Department and the American aid agency and were shared with The New York Times on the condition of anonymity because the figures were intended to be private.

Relief workers said they were alarmed and bewildered as to why the vast majority of the money was sitting unspent.

“Little to no humanitarian assistance has reached those on the front lines of this crisis in the world’s most fragile context,” executives at 27 relief organizations wrote to the aid agency’s acting administrator, John Barsa, in a letter dated Thursday.

“In spite of months of promising conversations with U.S.A.I.D. field staff, few organizations have received an executed award for Covid-19 humanitarian assistance,” the letter stated.

Most of the money is provided through the U.S. aid agency. A spokeswoman, Pooja Jhunjhunwala, said on Friday that the total amount made available so far to relief groups was $ 595 million, including $ 175 million in international disaster aid. But that included projected reimbursements for money that would be provided later — not funding that had already been delivered. The aid agency declined to disclose how much money had been delivered as opposed to promised.

Ms. Jhunjhunwala also described a rigorous review before releasing the funding to make sure it would be properly spent.

“We want to ensure that we are accountable for the effective use of Covid funds and are good stewards of U.S. taxpayers’ dollars,” she said in a statement.

Secretary of State Mike Pompeo has for months praised American generosity in helping the rest of the world respond to the coronavirus.

“America remains the world’s leading light of humanitarian goodness as well amidst this global pandemic,” he said in April. In May, Mr. Pompeo said, “The State Department is very focused on saving lives” in curbing the coronavirus. And on Thursday night, he said, “We have truly mobilized as a nation to combat the virus, both at home and abroad.”

Collectively, the aid agency and the State Department have committed more than $ 1 billion in pandemic assistance to more than 100 countries since April. But the vast majority of that has yet to go out the door, tied up in what people with knowledge of the funding described as a complex grant process that had been slowed by micromanagement and delayed decisions.

More than $ 500 million in additional funding — the balance of what Congress approved — has yet to even be committed to a humanitarian need, meaning it is likely to be months more before it is released.

“The funding pipeline is there — it’s ready to go,” said Bill O’Keefe, an executive vice president for Catholic Relief Services, one of the nongovernmental organizations that is delivering the humanitarian aid to needy nations. “But it is taking too long to turn on the tap.”

His organization has received about $ 10 million so far to help front-line coronavirus responders in the West Bank, Italy and Haiti. But he said the aid was being released “demonstrably slower” than in past global health crises, such as the Ebola outbreak in 2014 and 2015.

“We’re trying to get ahead of this situation; our goal is to get the prevention going early,” Mr. O’Keefe said. “Because the fewer cases there are, before things develop, the fewer people are going to suffer and die.”

The money provided by the State Department and the U.S. aid agency largely is to pay for messaging campaigns to educate people on how to protect themselves from the virus, to provide water and sanitation services like hand-washing stations, and to offer health services to refugees, migrants and other homeless people. Some of the funds have been spent on infection prevention and control.

Part of the delay in delivering the funds has been blamed on what officials in the Trump administration and in Congress described as an unresolved debate over whether the money can also be used to buy masks, gowns and other personal protective equipment for health workers who are treating coronavirus patients abroad.

Since April, the White House has been weighing whether to ban funding for protective medical gear overseas while the equipment is needed by health providers in the United States. Last month, the U.S. aid agency told some relief groups it could not use the money for personal protective equipment until the White House issued its policy.

Mr. Barsa has for weeks told relief groups that a decision is expected imminently, but until then, the ban applies to new aid contracts on a limited basis.

Nazanin Ash, a former senior official at both the U.S. aid agency and the State Department, said it had generally taken 30 to 45 days for humanitarian assistance funding to be delivered to relief organizations during the Ebola outbreak across West Africa and parts of Europe.

“Now it’s stretching to three to four months for funds to reach front-line responders, for a pandemic orders of magnitude greater that Ebola and for which prevention is the essential approach,” said Ms. Ash, who is currently a vice president at the International Rescue Committee.

The delay also comes as government officials and relief groups are trying to predict how much more money will be needed to confront the virus in the months and years to come, especially in poor and unstable nations that depend on American support.

Officials are considering projections of $ 5 billion to $ 12 billion for future global coronavirus response efforts that the United States funds. Congressional officials and relief workers voiced concern that vast amounts of additional resources would not be approved if the money that had already been appropriated continued to sit unspent.

Ms. Ash worked as a top staff member for foreign assistance at the U.S. aid agency under President George W. Bush, and later as a deputy assistant secretary of state under President Barack Obama. She said the agency had long been recognized as among the world’s most effective disaster aid responders, no matter its political leadership.

“Their absence on Covid response is a gaping hole,” she said.