United Nations - German Foreign Minister Guido Westerwelle on Tuesday met Iranian President Hassan Rouhani, welcoming a "new tone" from Tehran but demanding "substantial action" on its controversial nuclear programme.
"This is a good day for those who bet on a political and diplomatic solution," Westerwelle told journalists, calling Rouhani's speech to the UN General Assembly "encouraging".
He later met Iran's new leader, who has made diplomatic overtures in his country's nuclear standoff with the West.
The talks focused on Iran's nuclear programme and the civil war in Syria, diplomats said.
"We had a constructive discussion," Westerwelle said, stressing that he agreed with Rowhani that the use of chemical weapons is a "huge crime".
Western nations accuse Syria's President Bashar Assad of being behind the 21 August chemical attack near Damascus, which the United States estimates killed 1 400 people.
Westerwelle emphasized the "stark contrast" between the wording of Rouhani's speech and the fiery broadsides of his predecessor Mahmoud Ahmadinejad against Israel and the United States that prompted Western diplomats to walk out.
"The Iranians could be serious with a new constructive approach," he said but cautioned that Tehran must take concrete steps to prove its willingness to engage.
"It is critical that new substantial offers are made," Westerwelle added.
Germany's top diplomat also praised US President Barack Obama's speech to the General Assembly, who pushed for a "diplomatic path" with the new Iranian government.
Obama has sent a "strong signal" and offered a "window of opportunity" to end hostilities between Iran and the West, he said.
Westerwelle will participate in high-level talks on Iran's suspected nuclear programme on Thursday, joining counterparts from the United States, Britain, China, France, Russia and Iran.
On Syria, Westerwelle urged world leaders to make renewed efforts for a political process during their annual gathering in New York.
"There cannot be a military solution in Syria. Only a political solution can bring sustainable peace and stability," he said.
Westerwelle is scheduled to address the UN General Assembly on Saturday in what will likely be his last major appearance as foreign minister.
After four years at the helm of Germany's diplomatic corps, Westerwelle is set to leave office following his party's crushing defeat in Sunday's parliamentary elections.