German Foreign Minister Heiko Maas has called on European countries to join force and confront US President Donald Trump's "America first" policy, amid the ongoing trade war between the two sides.

In his first major policy speech since taking office, the new FM said the Wednesday that the European Union should try hard to establish a “balanced partnership” with Washington.

That would require the EU to with Washington where possible, fill the voids in areas where the US is withdrawing, and pushing back where it is crossing red lines, the top diplomat added.

“We Europeans have to act as a conscious counterweight when the US crosses red lines,” he said at an event organized by the pro-European organization United Europe in Berlin. “Where the US government aggressively throws into question our values and interests, we have to react more robustly.”

He named Trump's pullout of the Paris climate deal as well as the 2015 Iran nuclear deal and threats of imposing sanctions on European partners as some of the challenges posed by the current US administration.

Protectionism was another key issue between the two sides he said, referring to Trump's introduction of 25-percent and 10-percent import taxes on European steel and aluminum respectively.

Jean-Claude Juncker, head of the European Commission, said earlier this month that the bloc was prepared for immediate punitive measures, including tit-for-tat tariffs that would affect some $7.5 billion worth of US exports.

French President Emmanuel Macron has called the decision “illegal” and a “mistake," likening it to the kind of protectionist policies that some governments were making in the pre-World War Two era.

Mass also warned against attempts by "foreign powers" to split the EU and said the bloc should move toward majority and away from unanimous decision-making.

He also called on the EU to step up its reach to former Soviet republics and said Germany and France can take the front seat in reforming Europe.