The best way to address international concern about Iran's role in the region and its ballistic missile programme is within the framework of the nuclear deal, even after the United States pulled out, German Chancellor Angela Merkel said.
"The question is whether you can talk better if you terminate an agreement or if you stay in it ... we say you can talk better if you remain in it," Merkel told lawmakers in the Bundestag lower house of parliament on Wednesday.
European powers this week vowed to keep the 2015 nuclear deal alive without the United States by trying to keep Iran's oil and investment flowing, but admitted they would struggle to provide the guarantees Tehran seeks.
The deal between Iran and six world powers lifted most international sanctions in 2016 in return for Tehran curbing its nuclear programme, under strict surveillance by the U.N. nuclear watchdog.
"This agreement is everything other than ideal, but Iran is, according to all the knowledge of the international nuclear authorities, sticking to the commitments of the agreement," said Merkel.
Last week, U.S. President Donald Trump abandoned the pact he branded "the worst deal ever" and reimposed U.S. sanctions on Iran.
"Despite all the difficulties that we have these days, the transatlantic relationship is and remains paramount," Merkel told lawmakers. "But these transatlantic relationships also must be able to deal with differences of opinion."