U.S. President Barack Obama says he has spoken by phone with Iranian President Hassan Rouhani, the first direct contact between the leaders of the United States and Iran since 1979.
Mr. Obama told reporters at the White House Friday that he and Mr. Rouhani had constructive talks.
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 path to a meaningful agreement will be difficult and at this point both sides have significant concerns that will have to be overcome but I believe that we have a responsibility to pursue diplomacy and that we have a unique opportunity to make progress with the new leadership in Tehran. I also communicated with President Rouhani my deep respect for the Iranian people.''
A senior U.S. administration official said the White House received word Friday morning that Mr. Rouhani wanted to talk with President Obama before the Iranian leader departed New York, where he was attending the Untied Nations.
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.
Mr. Rouhani said he did not meet with Mr. Obama this week on the sidelines of the General Assembly because there was not enough time to plan such a meeting.
A senior U.S. official said the United Sates has been in touch with other governments about Friday's phone conversation, including Israel and Gulf nations, and with members of Congress.
The official said Israel has "every right to be skeptical" given the history of inflammatory statements by Iran, but said that the United States is trying to achieve an objective that would serve the security interests of the U.S., Israel and world.
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.
Also Friday, Iranian officials held talks with the International Atomic Energy Agency, their first meeting with the U.N. body since Mr. Rouhani was elected.
IAEA chief negotiator Herman Nackaerts called the talks in Vienna "very constructive" and said the two sides would meet again next month.
The focus of the meeting was to discuss suspicions that Iran has been taking steps to build a nuclear weapon. The IAEA wants to resume an investigation into Iran's alleged atomic bomb research.
Earlier this week, Mr. Rouhani said at the General Assembly Iran has a right to pursue a nuclear program for peaceful purposes.
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.