SMOOT-HAWLEY-DONALD:

The president's move, relying upon a little-used provision of U.S. trade law, is expected to trigger immediate legal challenges by U.S. trading partners at the World Trade Organization and invite retaliation against American exports.

Trump also turned back pleas from companies that are heavy users of steel and aluminum, including automakers, who warn that higher prices will hurt their sales and potentially lead to layoffs. In 2002, the last time the United States imposed steel tariffs, steel users blamed the measures for the loss of up to 200,000 jobs.

Sen. Roy Blunt (R-Mo.), a member of the Republican leadership, said before the announcement that he feared the tariffs will hurt companies in his home state.

"I continue to be concerned about what other countries do in response to that," Blunt said. "In our state, we make steel and aluminum, but we continue to buy a lot more than we make. Things like sheet aluminum that you use to make boats with, we make a lot of boats, it's not available in the United States."

The United States already has 169 trade taxes in place on various types of imported steel, including 29 on Chinese products. Some of the nation's largest steelmakers, which sought the new tariffs, also are in good shape financially. Nucor reported a $1.1 billion profit last year.

"Import taxes on steel and aluminum will raise the prices of those products, which in turn will raise the price of doing business for U.S. manufacturers," said economist Christine McDaniel of George Mason University's Mercatus Center. "There are more people in U.S. manufacturing sectors that rely on steel than there are in the U.S. steel industry. In terms of the economics, the trade-off does not make sense."

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