President Donald Trump said Monday, March 5, that he is not backing down on his plan to impose tariffs on steel and aluminum imports even though research suggests steel tariffs would hurt some American automakers profitability.

The president loosely outlined his plan last Thursday, saying that he is looking to impose a global 25% tariff on steel imports and a 10% tariff on aluminum imports. While many details have yet to be revealed, Trump suggested on Twitter that Mexico and Canada may be exempt from the tariff -- "if new & fair [North American Free Trade Agreement] is signed."

Trump is arguing that the U.S. needs these tariffs because "our Steel and Aluminum industries are dead," but the plan may cost American corporations.

We are on the losing side of almost all trade deals. Our friends and enemies have taken advantage of the U.S. for many years. Our Steel and Aluminum industries are dead. Sorry, it's time for a change! MAKE AMERICA GREAT AGAIN!

— Donald J. Trump (@realDonaldTrump) March 5, 2018

"Steel is the primary material used by automobile manufacturers Ford (F) and General Motors (GM) ," Goldman Sachs analysts, including Chief U.S. equity strategist David Kostin, wrote in a March 2 research note. "Based on 2017 production mix, if the proposed tariff of 25% on imported steel translates into a similar magnitude of increase in steel prices, it would impact each firm by roughly $1 billion, representing 12% and 7% of their 2017 adjusted operating income, respectively."

Separately, Barclays analyst Dan Levy explained that the potential import tariffs have "meaningful implications" for the automotive industry as it accounts for roughly a quarter of U.S. steel consumption.

"However, we do think the initial reaction is overdone in what is likely to be about a 30-basis point to 40-basis point margin headwind to automotive manufacturing in the U.S. for our [original equipment manufacturers] (F, GM, FCA) -- but as we have learned with other macro shocks in the past, we can't disagree with the fast money who sells first and asks questions later," Levy wrote in a March 5 research note.

Over the last five trading days, shares of Ford Motor Co. fell 2.8%, Fiat Chrysler Automobiles N.V. (FCAU) stock declined 7.5% and General Motors Co. dropped about 9.1%. Investors really began selling the stocks following Trump's announcement on Thursday.

Ford said that even though it buys the vast majority of its steel and aluminum for U.S. production in the U.S., the tariffs could "result in an increase in domestic commodity prices -- harming the competitiveness of American manufacturers," according to a report by CNBC's Phil LeBeau.

General Motors, meanwhile, said it needs to better understand the details around the president tariff announcement, "but bottom line is we support trade policies that enable U.S. manufacturers to win and grow jobs in the U.S." The company also said it purchases over 90% of its steel for U.S. production from domestic suppliers.

Fiat Chrysler did not immediately respond to a request for comment on Trump's tariff plan.

Taking a look at overseas automakers, particularly the ones that have a large U.S. presence, Evercore ISI sees it affecting German carmakers.

"At the moment, we presume that (Trump's auto import tax threat) is merely sabre rattling," Evercore analysts wrote in a note, obtained by Reuters. "However, were it to materialize into policy, under our coverage, the greatest financial impact would likely be at BMW (BMWYY) , followed by VW (VLKAY) and Daimler (DDAIF) ."

The president of Germany's car-makers' trade group, Verband der Automobilindustrie, Bernhard Mattes, expressed concerned about the tariffs.

"Punitive duties can't be the answer," said Mattes, according to a separate Reuters report.

"A trade war between the USA and Europe must be avoided at all costs," Mattes said. "In such a trade war there are only losers on all sides."

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