Last week, the Trump administration cited a Korean War-era law to justify banning exports of protective masks made in the United States, while ordering American companies that produce such wares overseas to redirect orders to their home market. One American company, 3M, said halting planned shipments of masks overseas would imperil health workers in Canada and Latin America. On Monday, 3M said it struck a compromise with the government that will send some masks to the United States and some overseas.

In recent weeks, Turkey, Ukraine, Thailand, Taiwan, Indonesia, Bangladesh, Pakistan, South Africa and Ecuador have all banned the export of protective masks. France and Germany imposed bans on masks and other protective gear, lifting them only after the European Union barred exports outside the bloc. India banned exports of respirators and disinfectants.

Britain has prohibited exports of hydroxychloroquine, an anti-malarial drug now being tested for potential benefits against the virus. Hungary has banned exports of the raw material for that drug and medicines that contain it.

“The export bans are not helpful,” said Mariangela Simao, assistant director general for medicines and health products at the World Health Organization in Geneva. “It can disrupt supply chains of some products that are actually needed everywhere.”

President Trump has been especially aggressive in securing an American stockpile of hydroxychloroquine, disregarding the counsel of federal scientists who have warned that testing remains minimal, with scant evidence of benefits.

India is the world’s largest producer of hydroxychloroquine. Last month, the government banned exports of the drug, though it stipulated that shipments could continue under limited circumstances.

“In this situation, each country has to take care of itself,” said Satish Kumar, an adjunct professor at the International Institute of Health Management Research in New Delhi. “If we are not able to take care of our population, it will be a very critical situation.”