German Foreign Minister Sigmar Gabriel said Sunday that he feared US President Donald Trump would quit the Iran nuclear deal next week.
Trump is a stern critic of the 2015 accord, which he has called "the worst deal ever", and US officials say he intends to tell US Congress next week that Tehran is not honouring its side of the bargain.
"The United States is likely to quit the Iran agreement next week -- that is my great concern," Gabriel was quoted as saying by national news agency DPA.
However Gabriel said Germany remains committed to the agreement, which Berlin helped negotiate, to stop Iran from building a nuclear bomb.
Gabriel, speaking at a state election campaign event, said his question to Washington was: "What good will come of us treating Iran as though it is developing nuclear weapons after all? ... Nothing."
He accused the US administration of "replacing the rule of law with the law of the strongest".
"And that is a great danger for us because if the United States of America takes that course then the world will change," he said.
Trump is expected to announce that he is "decertifying" Iran's compliance with the agreement it signed to limit its nuclear programme in exchange for sanctions relief.
US officials insist this will not sink the deal itself but open the way for Congress to possibly develop new measures to punish other aspects of Iran's behaviour.
Resumed sanctions could derail the accord negotiated with Tehran by former president Barack Obama and other major world powers.
Congress requires the president to certify Iranian compliance with the deal every 90 days. The next date certification date is October 15.
Under the law, Congress would then have 60 days to decide whether to reimpose sanctions lifted by the deal.