Manufacturing giant 3M pushed back Friday against criticism from President Donald Trump over production of face masks that are badly needed by American health care workers.

3M said the administration asked it to stop exporting medical-grade masks to Canada and Latin America, which the company said raises “significant humanitarian implications” and will backfire by causing other countries to retaliate against the U.S.

The N95 masks, also called respirators, provide more protection against the new coronavirus than ordinary surgical masks. Governors and hospital officials around the country have warned of a dire shortage of masks and other protective gear that protects health care workers treating people with COVID-19, the disease caused by the new coronavirus.

The unusual but not unprecedented spat between the president and a leading American manufacturer broke out after Trump ordered 3M to produce as many N95 masks as administration officials believe are needed for the U.S.

The order directed heads of the Homeland Security Department and Federal Emergency Management Agency to use their authority under the 1950 Defense Production Act to acquire the “appropriate” number of N95 respirators from 3M and any of its affiliates.

The president followed up the order with a barbed tweet at the Minnesota-based manufacturer.

“We hit 3M hard today after seeing what they were doing with their Masks. ‘P Act’ all the way. Big surprise to many in government as to what they were doing – will have a big price to pay!” Trump tweeted on Thursday night.

The company responded Friday, saying it has been producing as many masks as possible for the U.S. market “over the last several weeks and months.” The company added that it has been working with the Trump administration since last weekend and has shipped masks that it produces overseas back to the U.S., including 10 million N95 masks 3M made in China.

Then 3M went further, criticizing Trump’s order.

The company said there are “significant humanitarian implications of ceasing respirator supplies to healthcare workers in Canada and Latin America, where we are a critical supplier of respirators.”

Canadian Prime Minister Justin Trudeau said Canada also sends essential health supplies and workers to the United States, and blocking exports of 3M would be a mistake.

“I think of the thousands of nurses who cross the bridge in Windsor to work in the Detroit medical system every day,” Trudeau said. “These are things American rely on..”

Doug Ford, premier of Ontario province, said he protested to U.S. Trade Representative Robert Lighthizer, expressing concern that Trump could create a shortage of masks for Canadian doctors and nurses.

“The health and well-being of our frontline workers depend on these essential medical items and now more than ever our countries need to work together to combat COVID-19,” Ford tweeted.

3M also said that “ceasing all export of respirators produced in the United States would likely cause other countries to retaliate and do the same, as some have already done. If that were to occur, the net number of respirators being made available to the United States would actually decrease. That is the opposite of what we and the Administration, on behalf of the American people, both seek.”