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Iran has a new president, and the White House is greeting him with cautious optimism.

President Hassan Rouhani was sworn in on Sunday, officially succeeding Mahmoud Ahmadinejad, the outgoing Iranian president who was term-limited this year.

Rouhani won the country's last presidential election by a landslide in June. A moderate cleric and former nuclear negotiator, Rouhani has pledged more transparency in Iran's nuclear program and increased trust with other countries.

"We note that President Rouhani recognized his election represented a call by the Iranian people for change, and we hope the new Iranian government will heed the will of the voters by making choices that will lead to a better life for the Iranian people," White House Press Secretary Jay Carney said, in a statement released by the press office, congratulating the people of Iran for participating in the June election.

"The inauguration of President Rouhani presents an opportunity for Iran to act quickly to resolve the international community's deep concerns over Iran's nuclear program," Carney said. "Should this new government choose to engage substantively and seriously to meet its international obligations and find a peaceful solution to this issue, it will find a willing partner in the United States."

Rouhani himself called his election win a "victory of moderation."

Rouhani, however, won't fully control whether Iran budges on its nuclear program. As was the case under president Ahmadinejad, Iran is ultimately led by Ayatollah Khamenei, who holds the title of supreme leader of the Islamic Revolution and serves as the final arbiter of major decisions.