President Donald Trump's tit-for-tat trade war keeps heating up. The European Union announced Wednesday it will in July start imposing a sweeping round of tariffs on $3 billion worth of U.S. products in retaliation for the White House's decision to hit European steel and aluminum products with duties.

"This is a measured and proportionate response to the unilateral and illegal decision taken by the United States to impose tariffs on European steel and aluminum exports," EU Commissioner for Trade Cecilia Malmström said in a statement.

The commission cited WTO rules that it said allow for proportional counter-tariffs, and endorsed a list of goods it had previously submitted to the organization.

"We regret that the United States left us with no other option than to safeguard EU interests," said Malmström.

The list includes a 25 percent tariff on imported U.S. steel and aluminum, and proposes duties on a hodgepodge of over 100 items, including bourbon, motorcycles, peanut butter, cranberries, orange juice, porcelain tableware, fishing vessels, plasma cleaner machines for removing contaminants from electron microscopy specimens, and digital flight-data recorders.

Earlier this month, Trump announced tariffs of 25 percent on steel and 10 percent on aluminum imported from trade partners Canada, Mexico, and the EU, citing national security concerns.

The United States must, at long last, be treated fairly on Trade. If we charge a country ZERO to sell their goods, and they charge us 25, 50 or even 100 percent to sell ours, it is UNFAIR and can no longer be tolerated. That is not Free or Fair Trade, it is Stupid Trade! — Donald J. Trump (@realDonaldTrump) June 2, 2018

The perceived imbalance in trade relations where other countries impose higher duties on U.S. goods than we levy on theirs was a campaign issue for then-candidate Trump.

Last April, Trump had ordered the Commerce Department to study the impact of steel and aluminum imports on national security under rarely used sections of the Trade Expansion Act.

In February, Commerce Secretary Wilbur Ross announced that the department had concluded that the imports did "threaten to impair the national security." It cited U.S. steel employment dropping by over one-third and overproduction by China.

The department gave Trump several recommendations, including a global tariff on steel and aluminum imports for all countries. The report said the measures would increase domestic production to levels needed for "long-term viability."

"We’ll be imposing tariffs on steel imports and tariffs on aluminum imports,” Trump told metals industry executives at the White House in March. “...you’re going to have protection for the first time in a long time."

Statistics from the U.S. International Trade Commission show that steel imports to the U.S. have fallen 22 percent in 2017 from their recent peak in 2014.

Remy Nathan, a spokesman for the Aerospace Industries Association, a trade organization representing aerospace manufacturers, said the group was worried about how the trade war would impact the industry.

"While we understand the administration’s focus on fair trade, the imposition of tariffs presents a significant threat for retaliation from other countries towards U.S. aerospace products, and our industry relies heavily on exports for its success," Nathan told NBC News.

"As trade negotiations continue, we encourage the administration to maximize the economic benefits of aerospace trade for American workers by identifying sustainable, multilateral measures to address aluminum and steel overcapacity in the global marketplace," said Nathan.

Other U.S. manufacturing companies and trade organizations did not respond to an NBC News request for comment.