Former German chancellor Gerhard Schroeder held talks Monday with top officials in Tehran on boosting trade links and Iran's diplomatic crisis with Saudi Arabia.
The visit comes ahead of the expected implementation of a nuclear deal with Iran that will open its economy to Western investment after years of sanctions on its banks and key industries.
"We envisage a good future for Iran-Germany relations after the final implementation of the nuclear deal," he told Foreign Minister Mohammad Javad Zarif, according to an official statement from Iran.
"German companies and business owners are ready to participate in all economic and industrial fields" in Iran, he said.
Schroeder also stressed Iran's role in regional peace and security.
"After the closing of the nuclear file, Europe and Germany hope to make utmost use of Iran's great potential to solve regional crises," he said.
Zarif said Tehran was entering "a new phase of relations with Germany".
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Schroeder and Zarif also spoke about Saudi Arabia, which has severed diplomatic ties with Iran in a row over the execution of a Shiite cleric. The execution triggered protests and an arson attack at the Saudi Arabian embassy in Tehran.
"Extremism is the real threat in the region, the ideological and financial sources of which are rooted in Saudi Arabia," Zarif said.
Schroeder was to meet the ministers of oil and transport, and President Hassan Rouhani, on Tuesday, a German embassy official said.
Schroeder is the honorary chairman of NUMOV, the Berlin-based German Near and Middle East Association, which works to boost trade.
Germany was the first member of the P5+1 countries (Britain, China, France, Russia and the United States plus Germany) to send a major trade delegation to Tehran after the nuclear deal was struck on July 14 last year.
That trip was led by Sigmar Gabriel, Germany's economy minister and Chancellor Angela Merkel's deputy.
Iran has said it needs tens of billions of dollars of investment and Western technology to revive projects in its oil, gas and petrochemical industries, which have suffered under sanctions.
The Islamic republic's 78 million population and educated workforce has long been seen as untapped, and its energy sector is considered ripe for deals.
With the fourth-largest oil reserves and the second in gas, Iran has the biggest combined energy deposits in the world.