BRUSSELS, March 6 (Xinhua) -- The European Union (EU) on Monday threatened to take retaliatory action by charging duty on American products if U.S. President Donald Trump imposed tariffs on European steel and aluminum.

EU Commissioner for Trade Cecilia Malmstrom said U.S. Levi's jeans and bourbon could be hit with a 25-percent import tax. Harley-Davidson motorcycles are also on a draft list of American goods to be taxed, according to the EU.

Malmstrom said the U.S. measures would have a negative impact on transatlantic relations and global markets.

Levi Strauss & Co., known worldwide for its iconic jeans, said it was strongly against trade barriers.

"We support open markets and free trade where everyone plays by the rules. Unilateral tariff impositions risk retaliation and destabilizing the global economy, in which case American brands, workers and consumers will ultimately suffer," a spokesperson told the media.

Trump announced last Thursday that the United States is set to impose 25 percent tariff on steel imports and 10 percent on aluminum.

Shortly after Trump's announcement, European Commission President Jean-Claude Juncker responded by saying that the EU would "react firmly and commensurately" to defend its own interests.

"The EU has been a close security ally of the U.S. for decades. We will not sit idly while our industry is hit with unfair measures that put thousands of European jobs at risk... The EU would react adequately and that's what we will do," Juncker said.

British Prime Minister Theresa May also told Trump Sunday that she has deep concerns about his tariff decision.

German Foreign Minister Sigmar Gabriel has called for a strong EU response, saying the move by Washington was "not at all acceptable" and urging Trump to rethink.