Enlargepengpeng/Getty Images Minnesota manufacturing giant 3M warned Friday that a Trump administration order reserving US-made N95 masks for the US market could backfire. Demand for these masks, also known as respirators, has surged in recent weeks because they help protect health care workers from contracting COVID-19. "Ceasing all export of respirators produced in the United States would likely cause other countries to retaliate and do the same," a 3M statement warned. "If that were to occur, the net number of respirators being made available to the United States would actually decrease." The statement was a response to President Trump's Thursday decision to invoke the Defense Production Act against 3M. The 1950 law gives the president broad powers to order US companies to devote manufacturing capacity to products that are essential to national defense. Trump invoked the law last week to order GM to manufacture ventilators. (GM was already planning to do so, but Trump said i..