European Council President Donald Tusk has hit back at the US President, saying "trade wars are bad and easy to lose" as the bloc prepares to retaliate against Donald Trump’s president's planned steel and aluminium tariffs.

"President Trump has recently said and I quote, 'trade wars are good and easy to win.' But the truth is quite the opposite. Trade wars are bad and easy to lose," Mr Tusk told a press conference in Luxembourg.

The European Union said it would strike back against the threatened tariffs, with counter-measures against flagship US products such as peanut butter, orange juice and bourbon whisky.

"Certain types of bourbon are on the list as are other items such as peanut butter, cranberries, orange juice," EU trade commissioner Cecilia Malmstroem told reporters after the European Commission, which handles trade matters for the bloc, discussed the tariffs.

Meanwhile, German Deputy Economy Minister Matthias Machnig also warned against premature reactions to Mr Trump’s threat to impose a 25% tariff on car imports.

Mr Machnig, speaking on the sidelines of a conference in Berlin, said the latest comments showed the danger that trade conflicts could result in escalating rhetoric, which would serve no one.

"I recommend waiting to see what is decided," Mr Machnig said.

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Separately, major trading partners of the United States expressed both commercial and systemic concerns about its tariffs plan and said they feared tit-for-tat trade actions, a World Trade Organisation (WTO) spokesman said.

China kicked off the debate about the planned tariffs on steel and aluminium at the closed-door meeting.

Delegations taking the floor included the EU, Canada, Turkey, Russia, Australia, South Korea, Japan, Mexico, India and Brazil.

"We fear that the United States may be opening a Pandora's Box that we would not be able to close," a trade official quoted Canada's ambassador as saying.