According to S&P Global Platts, prices for American-made hot-rolled coil steel, the industry benchmark, jumped 41 percent in the first half of 2018 and then fell about 21 percent from that peak in the second half of the year. That trend is likely to continue this year.

“Steel prices remain under pressure to begin 2019,” said Michael Fitzgerald, a metals pricing specialist at S&P Global Platts. “Typical seasonal improvements following the slower holiday period are yet to take hold as domestic steel buyers no longer fear a supply crunch.”

American businesses and trade groups have repeatedly urged the Trump administration to remove the tariffs, arguing they hurt domestic companies, not competitors, and will ultimately undercut economic growth.

“Tariffs are taxes paid for by American families and American businesses — not foreigners,” said Thomas J. Donohue, the president of the U.S. Chamber of Commerce.

American steel makers are feeling the pressure. Despite strong earnings in 2018, the stock prices of steel companies have been in a deep slump as investors fret that they are being propped up by government support that will be temporary. In the last year, shares of AK Steel are down 56 percent, US Steel is down 46 percent, Steel Dynamics is down 29 percent and Nucor’s stock is down 18 percent.

John J. Ferriola, the chief executive of Nucor, said that the falling stock price is head-scratching because he believes that the industry is on solid footing. While Mr. Trump’s tariffs have provided a “tailwind,” a strong economy, tax cuts and anti-dumping measures put in place by the Obama administration have revived the steel industry, Mr. Ferriola said.

“There’s a lot of doomsday talk about the tariffs and a lot of misinformation,” Mr. Ferriola said in an interview. “I keep hearing about how it is driving down demand and putting our customers out of business. We had a record year last year, and many of our customers also had a record year.”