"We consider this as being against international law, plain and simple," Brigitte Zypries told the Funke Mediengruppe newspaper chain.
"Of course we don't want a trade war. But it is important the European Commission now looks into countermeasures," she added, Reuters reported.
The German government and business leaders have said the new sanctions passed this month by the US House of Representatives could prevent German companies from working on pipeline projects that they say are essential to Germany's energy security.