Tehran has been able to bankroll a growing military presence in countries like Syria and Yemen because sanctions had been lifted in exchange for its halt in nuclear enrichment activities, Netanyahu argued.

Iran wants to "basically conduct a religious campaign in largely Sunni Syria and try to convert Sunnis," said Netanyahu at a joint press conference after talks with Chancellor Angela Merkel.

"This will inflame another religious war -- this time a religious war inside Syria and the consequences will be many, many more refugees and you know where exactly they will come," he warned.

More than a million asylum seekers, with Syrians making up the biggest group, have arrived in Germany since 2015, unsettling some Germans.

Netanyahu's comments reflected the reason that had largely led to Merkel's poor score at general elections in September. The Israeli leader was in Berlin on his first stop of a European tour to persuade EU leaders to follow the United States and quit the nuclear deal.

Germany, France and the United Kingdom are three of the signatories of the 2015 Joint Comprehensive Plan of Action (JCPOA) between world powers and Iran, aimed at keeping Tehran from acquiring nuclear weapons.

They have said that they remain committed to the landmark accord after US President Donald Trump pulled his country out last month.