Some of the nation’s largest farm groups, with strong ties to Wisconsin, have urged President Donald Trump to not place restrictions on imports of steel and aluminum because it would backfire against U.S. food and agriculture exports.

In a letter sent to the Trump administration Tuesday, 18 groups, including the American Farm Bureau and the National Milk Producers Federation, warned that “the aftermath of restrictions on steel and aluminum could be disastrous for the global trading system and for U.S. agriculture in particular.”

Some of the countries that export metals to the United States also are large importers of U.S. agricultural products, including grain, livestock and dairy commodities.

“The potential for retaliation from these trading partners is very real,” the groups said.

This spring, Trump ordered the Commerce Department to investigate imports of steel and aluminum that have flooded the marketplace and hurt American metal manufacturers.

The president has tapped a seldom-used trade law that would allow him to impose penalties on steel and aluminum imports if the Commerce Department determines they jeopardize national security.

U.S. steel mills and labor unions have said they support the effort, saying it’s about fair trade as well as the nation’s security interests.

“Many foreign competitors receive aid from their governments that is banned under trade rules they agreed to abide by. This includes free loans from state-owned banks, free land from local governments and state-subsidized raw materials,” Leo Gerard, president of the United Steelworkers union, said in a statement last week.

But the farm groups worry that every country with a market-sensitive industry could find a national security reason to circumvent trade deals, no matter how flimsy the reason might be.

The groups urged the administration to “avoid igniting…