Cleric Hassan Rohani, who is widely seen as a reformer, took the oath of office as Iran's new president Sunday, officially replacing hard-liner Mahmoud Ahmadinejad.
The inaugural ceremony was attended by top political leaders from over 55 nations, including China and North Korea, according to the Islamic Republic News Agency.
Rohani, 64, has promised economic reform and an end to Iran's international isolation.
Following his election on June 14, Rohani stressed the importance of dialogue with the international community, promising to pursue a "constructive relationship" and mend international ties.
He called for "moderation and prudence" and promised to reduce tensions with the West, which has been pressuring Iran to scrap its suspected nuclear weapons program.
On the country's nuclear program, Rohani -- a former nuclear negotiator for Iran -- said he is ready to increase transparency. He has blamed Ahmadinejad's hard-line policy for bringing hardship as a result of international sanctions.
Israel's Prime Minister Benjamin Netanyahu, however, described Rohani in an interview as a "wolf in sheep's clothing," urging Western nations to abandon their "illusion" that the new Iranian president is a moderate.
Israel says while Rohani may have won the votes of reform-minded voters, he was endorsed by the Supreme Leader of the Islamic Revolution Ayatollah Ali Khamenei and has long been part of the ruling clerical establishment.
Former President Ahmadinejad has repeatedly called for the destruction of Israel.
Tehran has been subject to stiff economic sanctions over its nuclear program imposed by the U.N. Security Council, the United States and its European allies.