Sigmar Gabriel made the remarks on January 11 in Brussels before a meeting with the foreign ministers of Iran, Britain, and France as well as EU foreign policy chief Federica Mogherini.
Gabriel, an outspoken critic of U.S. foreign policy since President Donald Trump took office a year ago, said Washington was right to address concerns about Iran's strategy in the Middle East.
But he said Iran has a 'difficult' role in the Middle East that must be discussed with the United States separately from the 2015 nuclear deal signed by Tehran and six world powers.
European powers were expected at their Brussels meeting on January 11 to reassure Iranian Foreign Minister Mohammad Javad Zarif that they remain committed to the nuclear deal.
'Sending A Message'
European diplomats said the aim of the Brussels meeting was 'to send a message to Washington that Iran is complying, and that it is better to have the nuclear agreement than to isolate Tehran.'
The meeting comes one day before a U.S. deadline requiring President Donald Trump to once again decide whether the U.S. will continue backing the deal.
Under the agreement, Iran has promised to curb nuclear activities in exchange for sanctions relief.
Many of Trump's top aides have reportedly been urging him to extend U.S. sanctions relief, but Trump remained reluctant on January 10.
Trump and key advisers were expected to meet later on January 11 to finalize the decision, which will be revealed on January 12.
Reports said U.S. Secretary of State Rex Tillerson, Defense Secretary James Mattis, and national security adviser H.R. McMaster were pressing Trump to sign the waiver granting Tehran relief.
Trump is a fierce critic of the accord and refused to certify Iran's compliance at the last deadline in October. But Trump has so far stopped short of withdrawing the United States from the accord.
Iran on January 10 warned it would pull out of the nuclear deal if the United States leaves.
'In case the Americans exit the deal, we will react in no time flat,' Majid Tacht Rawanchi, an adviser to President Hassan Rohani, was quoted as saying by Iran's state-run IRNA news agency.
The EU and other signatories to the accord -- Britain, China, Germany, France, and Russia -- continue to support the agreement.
Meeting with Zarif in Moscow on January 10, Russian Foreign Minister Sergei Lavrov vowed that Moscow would defend the agreement as a 'key contribution to regional stability and nuclear nonproliferation."
With reporting by AP, Reuters, AFP, and dpa