The issue, the Trump administration has argued, is not just one of jobs, wages, imports, and exports. It is also one of defense strategy: The U.S.’s reliance on imports leaves critical industries vulnerable to potential embargoes and trade actions by its enemies.

But trade experts see a number of problems with the White House’s argument for instituting tariffs on security grounds. Trump himself has repeatedly mentioned China’s trade practices as justification for the tariffs, for one. And the vast majority of the U.S.’s imports come from strong allies: Canada, South Korea, Mexico, Germany, Japan, and Brazil all export more steel to the United States than China does. “There is no question that steel and aluminum, materials used in the production of weapons and military systems, are vital for America’s military superiority,” a group of conservative think-tank scholars argued in response to then-potential tariffs in late February. “But it is not realistic to expect that foreign producers would withhold supplies in the case of a national security emergency.”

The flimsiness of Trump’s justification raises the risk of retaliation by the United States’ trading partners, many of whom have lobbied against the tariffs since the earliest days of the Trump presidency and are expressing their frustration with the tariffs now. Trade experts expect tit-for-tat actions, meaning lower sales for American businesses abroad. “If the United States goes down this path for steel and aluminum, there is little to prevent other countries from arguing that they too are justified to use similar exceptions to halt U.S. exports of completely different products,” argues Chad P. Bown of the Peterson Institute for International Economics, a Washington-based think tank broadly supportive of free trade. “Because this leads to a downward spiral and erodes meaningful obligations under international trade rules, justifying import restrictions based on national security is really the ‘nuclear option.’”

To that end, China has indicated that is ready to take action. “China urges the U.S. to use trade protection tools with restraint and comply with multilateral trade rules so as to make positive contribution to the international economic and trade order,” its Ministry of Commerce warned last month, adding, “China will definitely take necessary measures to safeguard its legitimate rights.”

The specter of a trade war undercuts Trump’s economic argument. The president has promised that steel and aluminum tariffs will bolster domestic industries and boost American payrolls, with some labor leaders and business executives in agreement. “U.S. steel and aluminum industries have been heavily injured by massive growth of excess capacity and overproduction in China and other countries,” argues Robert E. Scott of the Economic Policy Institute, a left-of-center think tank. “More than 13,000 U.S. jobs have been lost in aluminum since 2000—and 14,000 steel jobs disappeared in [the] last two years alone.” But America’s steel and aluminum industries simply do not employ that many workers. Restoring all those jobs would be but a blip in a monthly payroll report.