In normal times, rising exports would usually be welcomed by the European Union. In the current climate, it could mean aggravating an already strained relationship with the U.S. just as President Donald Trump weighs whether or not to impose tariffs on auto imports from Europe.

The EU's current account surplus with the U.S. grew by 50.1% in 2018 to €130 billion, while the surplus in goods reached €149.4 billion, according to European Central Bank data released April 4. U.S. imports of goods from the EU rose from $434.6 billion in 2017 to $487.9 billion in 2018, U.S. Census Bureau data show.

While trade negotiations with the EU are low on Trump's foreign policy checklist as he focuses on deals with China and Japan and an immigration spat with Mexico, the EU will likely come back onto Trump's radar as a mid-May deadline on deciding whether to invoke a national-security clause to implement tariffs approaches. The U.S. has surpluses with the EU in services and secondary income, but when it comes to trade deficits, Trump typically focuses his remarks only on goods.

"At some point, Trump is going to say this [negotiation] is not moving quickly enough and there will be a blast at Europe and he'll trot out these [deficit] numbers. And he'll probably threaten car tariffs again," William Reinsch, a senior adviser at the Center for Strategic and International Studies, said in an interview.

The U.S. Department of Commerce instigated a so-called Section 232 investigation into imports of automobiles and their parts on May 23, 2018, to determine whether the competition with the U.S. car industry is a threat to the country's security. The Commerce Department submitted the report to the White House in mid-February, giving Trump a 90-day deadline to decide whether to impose tariffs.

"Everybody's telling him not to," Reinsch said. "This appears to be a case where there's only one person in the world who thinks these tariffs are a good idea, and unfortunately, it's the person who makes the decision."

Trump's tariffs on Chinese goods were careful to avoid finished products, which would raise prices for consumers directly, and a tax on EU-assembled cars would do exactly that. But the lack of progress on talks with the EU may persuade Trump to play the auto card anyway.

The U.S. ramped up the tension with the EU on April 8 when it threatened tariffs on a range of European Union imports in retaliation against the bloc's subsidies to Airbus SE that the World Trade Organization said caused "adverse effects" to the U.S.

The U.S. Trade Representative is considering imposing duties on new helicopters, new aircraft and aircraft parts from Germany, France, Spain and the U.K. Also, on the list are food imports from the broader EU region. Any tariffs would come on top of duties already levied by the U.S. on European steel and aluminum.

The major sticking point in a potential trade agreement between the two economic superpowers is agriculture. In a statement to the Senate Finance Committee in March, U.S. Trade Representative Robert Lighthizer described talks with the EU as being in a stalemate. "The United States can't have a trade agreement with Europe that doesn't deal with agriculture, and their view is that they can't have one that does," Lighthizer said.

French farmers say 'non'

The U.S. is keen to sell its products into the 500 million-person EU market, partly to compensate U.S. farmers who have suffered from retaliatory tariffs in China, as well as lost sales to Japan due to Trump pulling out of the Trans-Pacific Partnership agreement.

"I spoke to one of Lighthizer's minions about agriculture," Reinsch said. "They said they genuinely don't believe they can get a [EU trade] bill through congress without mentioning agriculture."

But the EU membership — particularly France — is protective of its domestic industry and has explicitly ruled out including agriculture in the discussions.

"[Trump] could keep the threat of the car tariffs hanging for as long as possible and use it as leverage to put agriculture on the table," Marianne Schneider-Petsinger, geoeconomics fellow at think tank Chatham House, said in an interview. "But the draft negotiating mandate for the European Commission [to be signed off by member states] does not include agriculture; it only commits to industrial tariffs and conformity assessment."

Gary Hufbauer, a senior fellow at the Peterson Institute for International Economics, does not expect Trump to ramp up his rhetoric toward the EU until deals with other countries are complete, no sooner than 2020.

"My thinking is that once he wraps up things with China, he will turn to Europe. And I do expect the threats to ramp up," Hufbauer said in an interview. "I think he will use the widening surplus as more of an argument for the demands he’s putting on the table."