Speaking to broadcaster Deutschlandfunk on Friday, Brigitte Zypries said that if Mr Trump implemented the tax, it would be incredibly complex for the whole system and the adjustment would take a long time.
She said that one option for Germany would be to file a suit against the President at the WTO.
It is “clearly laid out” in WTO agreements that you are “not allowed to charge more than 2.5 per cent taxes on imports of cars”, she said.
She added that she’s banking on both the President’s “rationality” and the power of the law to make ensure that the tax does not come into effect.
Chancellor Angela Merkel and Mr Trump are meeting on Friday for the first meeting since the new US President took office. The two have so far had a strained relationship.
In 2015, Mr Trump tweeted that the German chancellor was “ruining Germany”.
Similarly, he compared his presidential opponent Hillary Clinton to Ms Merkel, saying she wants to “be America’s Angela Merkel and you know what a disaster the massive immigration has been to Germany and the people of Germany".
However, in 2016, Mr Trump picked Ms Merkel as his favourite world leader, despite his criticism of her position on refugees.
Germany's €50bn trade surplus with the US has also proved a source of tension between the two countries in recent months, according to Reuters.
"We know ourselves that that's a problem and we're working on it," Ms Zypries said on Friday.
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