Amano joined the negotiations between Iran and the Group 5+1 (Russia, China, the US, Britain, France and Germany), which resumed in Vienna's Coburg Hotel Saturday for clinching a lasting deal on Tehran's nuclear energy program.
Earlier, Iran's Foreign Minister Mohammad Javad Zarif, US Secretary of State John Kerry and French Foreign Minister Laurent Fabius arrived in Vienna for the talks.
Foreign ministers of Britain, Germany, Russia, and China as well as the European Union's foreign policy chief Federica Mogherini are also expected to join the high-profile talks later.
Iran and the Group 5+1 (alternatively known as the P5+1 or E3+3) have been negotiating over the past 22 months to hammer out a lasting accord that would end more than a decade of impasse over Tehran's civilian nuclear program.
On April 2, the two sides reached a framework nuclear agreement in Lausanne, Switzerland, with both sides committed to push for a final deal until the end of June.