By Chester Dawson and Josh Zumbrun 

President Donald Trump stood by his threats to levy sweeping tariffs on automobile imports as a way to extract concessions from trading partners, despite opposition from the industry and discontent in Congress with the White House's proposal.

Resistance to the tariffs is strong and growing. A coalition of foreign and domestic auto companies, along with auto dealers and auto-parts makers, released a letter on Wednesday urging Mr. Trump to refrain from the tariffs.

A bipartisan group of 149 House members also urged the president not to move forward with the tariffs. Auto unions were among the few industry players offering qualified support for the tariffs.

Still, at a cabinet meeting on Wednesday, Mr. Trump threatened "tremendous retribution" against the European Union, specifically mentioning auto tariffs, if his meeting with EU officials next week doesn't yield what he considers a fair auto trade deal.

Mr. Trump is seeking to refocus attention on his trade agenda, while his administration at the same time is contending with criticism over his comments this week on alleged Russian interference in the 2016 election.

The issue of auto tariffs is the subject of a Commerce Department hearing on Thursday and is expected to be high on the agenda of the July 25 White House visit by European Commission President Jean-Claude Juncker.

Mr. Trump, a Republican, has repeatedly threatened tariffs on imported autos and auto parts if European leaders don't make trade concessions. The threat also hangs over negotiations with Canada and Mexico over the North American Free Trade Agreement.

The Commerce Department hearings on Thursday are part of an investigation aimed at justifying the auto tariffs as necessary for U.S. national security. The administration, citing the rarely used 1962 Trade Expansion Act, also used the national-security justification earlier this year in imposing global tariffs on steel and aluminum imports.

If the plan is carried through, the tariffs on autos and auto parts would be Mr. Trump's biggest tariffs yet. In 2017, the U.S. imported $176 billion worth of passenger cars, $36 billion of trucks and $147 billion of auto components, according to Commerce Department data. The administration has threatened tariffs of 20% to 25%.

The invocation of national security has drawn objections from lawmakers. "We do not believe the imports of automobiles and automotive parts pose a national-security threat," the House members said in the joint letter sent Wednesday. "Rather, we believe the imposition of trade restrictions on these products could undermine our economic security," said the letter.

There has been growing discontent in the Senate, too. Sen. Lamar Alexander (R., Tenn.) said Wednesday: "These tariffs are dangerous. They are going to cost us jobs and lower our family incomes."

Mr. Alexander and Sen. Doug Jones (D., Ala.) said they would introduce legislation aimed at halting Mr. Trump's auto tariffs. Last week, the Senate voted 88-11 to give Congress a role in determining when tariffs are imposed on the basis of national security. The measure is considered largely symbolic because it contained no specifics.

Some support for the tariff proposals has come from union groups, which generally back Mr. Trump's trade policies and efforts to protect U.S. jobs and domestic production capacity. The United Auto Workers union -- which represents workers at General Motors Co., Ford Motor Co. and Fiat Chrysler Automobiles NV -- has expressed support for the administration's investigation, calling it "long overdue."

But the UAW stopped short of endorsing the tariffs and instead urged a more "targeted" approach, such as taking steps to stop the influx of auto investment in Mexico in recent years.

Auto industry officials, meanwhile, have grown increasingly alarmed at the prospect of adding yet another tariff to the ones already levied by the White House on aluminum, steel and some Chinese-made goods.

"Raising tariffs on auto and auto parts would be a massive tax on consumers, who buy or service their vehicles," according to an open letter to Mr. Trump that was jointly submitted by the industry's main lobbying groups, including trade organizations that represent the foreign and U.S.-based auto makers, as well as auto dealers.

The Alliance of Automobile Manufacturers, which represents 12 of the largest auto manufacturers, warned the tariffs risk triggering a negative "domino effect" that would harm U.S. workers and the broader economy, according to prepared remarks shared ahead of the Commerce Department hearing.

The Commerce Department will make a determination on the security threat and what remedies should be proposed, a process that could take several months. No final decision can be made until the process is complete.

Mr. Trump's remarks Wednesday made it clear he sees the tariffs as a tool in trade talks with Europe, Canada and Mexico. "If we don't negotiate something fair, then we have tremendous retribution, which we don't want to use," Mr. Trump said, adding: "Including cars, cars is the big one."

Mr. Trump has frequently cited the disparity between the 2.5% tariff that the U.S. charges for car imports and the 10% tariff imposed by the EU on imports there. Mr. Trump doesn't mention that the U.S. imposes a 25% tariff on imports of light trucks, compared with a 10% tariff from Europe.

In his remarks, Mr. Trump also cited EU trade barriers against U.S. agriculture as a source of concern. And he said he had a "good session" with Mexico on Nafta, which he has called unfair. He said that the U.S. may complete separate agreements with Mexico and Canada.

White House press secretary Sarah Sanders said Wednesday that talks on Nafta are ongoing, and no decisions have been made.

"If we can make a bilateral deal we are certainly happy to do that, but we are continuing conversations on both tracks," she said.

Mr. Trump has said he plans to use the 25% tariff threat as leverage in other trade negotiations, such as the Nafta talks. "If they're not fine, I'm going to tax their cars coming into America, that's a big one," Mr. Trump said earlier this month.

That has led some to question the impartiality of Thursday's hearing. "This is a show trial," said Adam Posen, president of the Peterson Institute for International Economics. "This is something where they predetermined the verdict and the schedule on which the verdict would be read."

Auto makers building cars in the U.S. and employing tens of thousands of workers would be hit by higher costs if the tariffs were enacted, analysts and car makers said.

Toyota Motor Corp. said it opposes the tariffs, because even though it builds cars in the U.S., it uses foreign-sourced parts that would be subject to the levy. For instance, about 30% of the parts used in a U.S.-built Toyota Camry come from outside the U.S. A tariff on those parts would increase the price of a Camry by $1,800, the company said.

"Our viewpoint on a 25% tariff on automotive and automotive parts is that it is something that is misguided," said Brian Krinock, senior vice president, vehicle plants, for Toyota North America. "We believe in the end the consumer will end up having to pay the additional costs."

GM also has said the proposed tariffs would raise its costs, hurt its global competitiveness and put U.S. jobs at risk.

--Michael C. Bender contributed to this article.

Write to Josh Zumbrun at Josh.Zumbrun@wsj.com

(END) Dow Jones Newswires

July 18, 2018 19:56 ET (23:56 GMT)