“We want to make sure the front-line health workers, wherever they are, are protected,” said Mr. Klosson, whose organization receives funding from the U.S. aid agency and the State Department.

“We’ve seen what’s happened in developed countries, where very advanced health systems and social safety nets have been overwhelmed,” he added. “Just imagine the challenges as this thing kind of multiplies in sub-Saharan Africa and places like that, with countries with much weaker health systems and much weaker social safety nets.”

The U.S. aid agency has shipped about 150,000 N95 masks and thousands of scrubs, coveralls and face shields to health care workers in Oregon from its warehouse in Dubai, United Arab Emirates. Andrew Phelps, Oregon’s director of emergency management, said last week that it “will make a huge difference in Oregon’s ability to fight this outbreak.”

In March, the aid agency was sending personal protective equipment from its own stockpiles to nations in need.

That changed after a meeting later in the month. Officials who were gathered from across the government were surprised to hear that those shipments were continuing and told the agency to stop, according to a senior administration official who spoke on the condition of anonymity.

A representative from the aid agency who was at the meeting asked for a memo to formalize the shipment freeze, the senior administration official said. Within weeks, and faced with a projected shortage in the Strategic National Stockpile of medical supplies, President Trump invoked the Defense Production Act to prohibit the export of face masks to other countries.