Separately, Germany's transatlantic coordinator, Juergen Hardt, told Reuters the usa government should have exempted its European allies from punitive tariffs imposed against steel and aluminium imports that were primarily aimed at China.
However, he exempted, at least temporarily, Mexico and Canada, and suggested the "great country" of Australia would also be spared, along with "possibly other countries as well" who were "real friends".
"We are an ally, not a threat", Katainen said.
The European Union said it would strike back against the threatened tariffs, with counter-measures against flagship U.S. products such as peanut butter, orange juice and bourbon whisky.
The European Union, the world's biggest trade bloc, chimed in.
"We need a clarity to the situation but it is also very clear that we are looking at an option to be excluded from high tariffs", Jyrki Katainen, Vice-President of the European Commission in charge of Jobs, Growth, Investment and Competitiveness, told a press conference.
Malmstrom told reporters the European Union was ready to complain to the World Trade Organization and retaliate within 90 days.
The EU's top trade official Cecilia Malmstroem will meet US Trade Representative Robert Lighthizer in Brussels along with Japanese Economy Minister Hiroshige Seko.More news: Serena Williams 'definitely' wants to have more kids with husband Alexis Ohanian
German Chancellor Angela Merkel urged dialogue and warned that "no one can win in such a race to the bottom".
EU Commissioner Cecilia Malmstrom, who coordinates policy for the world's biggest trading bloc, said she shared USA concerns about overcapacity in the steel sector but did not believe in tariffs as a way to solve the problem.
The EU exports around five billion euros' ($4 billion) worth of steel and a billion euros' worth of aluminum to the U.S. each year, and the European Commission, the bloc's executive arm, estimates Trump's tariffs could cost some 2.8 billion euros.
"The loss of exports to the US, combined with an expected massive import surge in the European Union could cost tens of thousands of jobs in the European Union steel industry and related sectors", Eggert said.
Trade tensions between Washington and Beijing have risen since Trump took office a year ago. Tariffs would "seriously impact the normal order of worldwide trade", the Commerce Ministry said. She also stated that the justification given by the US was highly unjust.
South Korea, the third largest steel exporter to the United States and a strategic ally on the Korean peninsula, called for calm.
While carrying a message to Washington to push forward a diplomatic breakthrough over North Korea, South Korea's national security office chief, Chung Eui-yong, requested US officials to support Seoul's request for a waiver, a presidential spokesperson said.