Trump set import tariffs on Thursday of 25 percent on steel and 10 percent on aluminum, to come into force in 15 days. He exempted Canada and Mexico, however, and held out the possibility of excluding other allies.
"Trump's policies are putting the order of a free global economy at risk," Zypries said in an e-mailed statement.
"He does not want to understand its architecture, which is based on a rule-based system of open markets. Anyone, who is questioning this, is jeopardizing prosperity, growth and employment," Zypries said.
Germany and its allies must now safeguard the free trade order and avoid being divided by Trump's offer to exempt some allies from the proposed tariffs, Zypries said.
The European Union and Japan urged the United States on Saturday to grant them exemptions from metal import tariffs, with Tokyo calling for "calm-headed behavior" in a dispute that threatens to spiral into a trade war.
US President Donald Trump set import tariffs on Thursday of 25 percent on steel and 10 percent on aluminum, to come into force in 15 days. But he exempted Canada and Mexico and held out the possibility of excluding other allies.
After meetings with US trade envoy Robert Lighthizer in Brussels, EU and Japanese trade officials said negotiations would need to continue.
Europe's trade chief Cecilia Malmstrom described talks with Lighthizer as "frank" and said they had not brought clarity on the exemption procedure. Talks would continue next week.
"As a close security and trade partner of the US, the EU must be excluded from the announced measures," she tweeted after bilateral and trilateral meetings.
Japanese Trade Minister Hiroshige Seko said he had expressed Japanese concern to Lighthizer and warned of major market disruption.
"We call for calm-headed behavior," he told reporters.
The EU and Japan also reiterated that their exports were not a threat to US national security, rejecting Trump's justification for imposing the tariffs.
Newspaper headline: EU, Japan start push for exemptions