A 15-minute telephone conversation between the presidents of the United States and Iran has ended a 35-year diplomatic freeze.
The phone call Friday between Barack Obama and Hassan Rouhani marked the first time the leaders of the two countries have talked since the Islamic revolution ousted the U.S.-backed shah in 1979.
Mr. Obama said the two leaders discussed "ongoing efforts" to reach an agreement on Iran's nuclear program.
Mr. Rouhani's English-language Twitter account announced the news of the historic conversation.
The two leaders spoke while the Iranian president was in a car in New York where he attended the United Nations and Mr. Obama was at his desk in the Oval Office.
President Obama said he believes the two countries can reach a comprehensive solution over Iran's nuclear program and that the conversation shows the possibility of moving forward.
A senior U.S. administration official said the White House received word Friday morning that Mr. Rouhani wanted to talk with Mr. Obama before the Iranian leader departed New York.
Earlier Friday, Mr. Rouhani said that Mr. Obama has struck a new tone that has left him optimistic about a quick settlement on the nuclear issue.
The Iranian leader said his election in June helped pave the way for better relations between Iran and the West.
A senior U.S. official said the United States has been in touch with other governments about Friday's phone conversation, including Israel and Gulf nations, and with members of Congress.
On Capitol Hill, House of Representatives Foreign Affairs Committee Chairman Ed Royce credited "damaging sanctions" for getting the Iranian leader on the phone with Mr. Obama, adding that pressure must be maintained.
Iran has long insisted its nuclear program is peaceful. The U.S. and some of its allies disagree, and have helped impose several rounds of sanctions that have battered Iran's economy.