Commission President Jean-Claude Juncker is due to meet US President Donald Trump to discuss the imposition of US tariffs on EU steel and aluminum and his threats to expand those measures to European cars.
"It is good that Jean-Claude Juncker will be in Washington tomorrow to talk and to seek a solution but we are not heading to negotiations with a pistol at our chest. I don't think threats bring us closer to a solution," Maas said, Reuters reported.
"We in Europe must stick together...I hope that we succeed in resolving this via consensus but we will not be threatened and climb down so easily," he told German public television.
Trump has complained about higher duties applied by the European Union on car imports and has described the bloc as a trade "foe".
EU officials say that while EU import duties for cars are heavier than those applied by the United States, the US rates for other products, including trucks, are higher. They say cutting duties for cars can only be part of a broader trade deal.
Maas, about to visit Japan and South Korea, who are also threatened by US tariffs, said no one had an interest in new and higher tariffs.
"In the end, all sides would lose, also the Americans," he said, adding he hoped that US officials would realize this.