U.S. Secretary of State John Kerry met with Iranian Foreign Minister Mohammad Javad Zarif in New York on April 27.
The two met on the sidelines of the five-year review conference of the Nuclear Nonproliferation Treaty.
The meeting comes as the United States and five other global powers try to secure a final nuclear deal with Iran by a June 30 deadline.
A U.S. State Department official said the two discussed those negotiations and described their meeting as "productive."
Earlier, Kerry told the UN conference that a deal would make the world a safer place.
Under a tentative deal reached on April 2, Iran agreed to cut the number of uranium enrichment centrifuges it operates and to allow more intrusive inspections by the International Atomic Energy Agency in exchange for sanctions relief.
Diplomats need to iron out details about the timing of sanctions relief and the future of Iran's atomic research and development program, among other issues.
Tehran denies it is secretly developing nuclear weapons, as many Western nations suspect.