The two shook hands in front of cameras before their closed-door meeting at the foreign ministry in Tehran, AFP reporters said.

The nuclear deal is "extraordinarily important" for Europe's security, Maas told reporters overnight after arriving in Tehran on the last leg of a regional tour that took him to Iraq, Jordan and the United Arab Emirates.

But he added: "We do not want Iran to have nuclear weapons."

The nuclear deal known as the Joint Comprehensive Plan of Action (JCPOA) was struck between Iran and six major powers -- Britain, China, France, Germany, Russia and the United States -- in 2015.

It saw Iran scale down its nuclear programme in exchange for sanctions relief.

But last year the United State unilaterally withdrew from the deal and reimposed sanction on Iran.

Tehran has urged Europe to uphold commitments made under the deal and help Iran circumvent US sanctions.

Iran has also threatened to scale down its nuclear commitments if its interests are not met.

According to Maas, Germany and its European partners "have made the greatest effort to meet (their) commitments".

He acknowledged that the economic benefits Tehran hoped for from the deal were now "more difficult to obtain" but urged Iran to fully respect the agreement.

It is in Iran's "political and strategic interest to maintain this agreement and the dialogue with Europe," he said.