BRUSSELS - US President Donald Trump's decision to impose a 25-percent tariff on steel and aluminum imports upon entering the United States, regardless of their country of origin, has sparked strong opposition across Europe.

European Commission President Ursula von der Leyen warned on Tuesday that US tariffs on steel and aluminum imports from the European Union (EU) "will trigger firm and proportionate countermeasures".

"Unjustified tariffs on the EU will not go unanswered," von der Leyen said in a statement. "The EU will act to safeguard its economic interests. We will protect our workers, businesses and consumers."

Addressing members of the European Parliament (MEPs) in Strasbourg on Tuesday, European Commissioner for Trade and Economic Security Maros Sefcovic said that the EU will respond "firmly and proportionately" to the tariffs imposed by the US.

"In our opinion the tariffs are unjustified, because they will lead to an increase in prices and inflation," Sefcovic said. Describing the move as a "lose-lose scenario", he warned that the tariffs were "economically counterproductive".

German Chancellor Olaf Scholz reaffirmed EU's stance on countermeasures. "If the US leaves us no other choice, the EU will respond with a united position," he said in a speech to the Bundestag on Tuesday.

However, he cautioned against escalating tensions. "I hope we can avoid the misguided path of tariffs and counter-tariffs, as trade wars ultimately come at the expense of prosperity on both sides," he added. He also warned that US tariffs could soon extend beyond steel and aluminum, posing a particular threat to Germany as Europe's largest exporting economy.

Dirk Jandura, president of the Federation of German Wholesale, Foreign Trade and Services (BGA), said in a statement that should Trump's tariffs take effect, the EU must respond with a unified position. He cautioned that a trade war could have "fatal" consequences.

Polish Prime Minister Donald Tusk said Tuesday that Poland is preparing for the potential impact of the US tariffs. "It is worth doing everything to avoid unnecessary trade and customs wars, because this brings negative consequences for producers and consumers," Tusk said before a government meeting.

Czech Industry and Trade Minister Lukas Vlcek told local media Tuesday that Europe needs to act in unison against the US tariffs. Given the size of the EU's trade with the US, a tariff war would not help anyone, he said.

Slovak Prime Minister Robert Fico said in a post on social media Monday evening that the imposition of high customs tariffs on steel and aluminum from Europe is a manifestation of Trump's distrust in the power of the EU, which he disrespects.

A new round of US protectionist policies could harm global trade, disrupt supply chains, and ultimately burden consumers in the US, Fabrizio Hochschild, former under-secretary-general of the United Nations (UN), told Xinhua.

"History shows that unilateral tariffs often provoke retaliatory measures, disrupting supply chains and undermining economic stability," Hochschild noted, emphasizing that trade disputes should be resolved through multilateral mechanisms like the World Trade Organization (WTO).

"In any case, the announced tariffs will harm American producers and consumers in the end," said Drago Patrlj, Croatian political analyst. "The world seems heading for a trade war, and it is extremely uncertain who will win and who will lose," he said, adding, "In fact, everyone will lose, it's just a question of who will lose more."