BERLIN - German companies are concerned that U.S. President Donald Trump is increasingly thinking only of America rather than just putting his country first, the head of Germany's DIHK Chambers of Commerce told media.

The United States has pulled out of the 2015 Iran nuclear deal and Germany has acknowledged it could be hard to protect companies doing business with Iran, as a senior U.S. official renewed a threat of sanctions against European firms.

German companies also face the prospect of possible extra levies - Trump imposed a 25 percent tariff on steel imports and a 10 percent tariff on aluminum in March but the European Union has been granted exemptions until June 1.

"America First now increasingly means America Alone," DIHK President Eric Schweitzer told the RND group of newspapers. "That makes German businesses really worried."

Nonetheless, a DIHK survey published earlier this month showed a record number of German companies believe economies in foreign markets where they do business will improve despite rising political and trade risks.

In January Trump said he would always promote "America First", as he expected other world leaders to do on behalf of their own countries, but added: "America First does not mean America alone. When the United States grows so does the world."

Schweitzer called for the EU to take a tough line in the trade dispute with the United States, saying while it was important to remain in dialogue over difficult conflicts, "we're moving in the wrong direction if we automatically react to new unreasonable demands with concessions."

Germany is Europe's biggest exporter to the United States.