U.S. Secretary of State John Kerry and Iranian Foreign Minister Mohammad Javad Zarif have discussed during talks in New York on September 21 the threat posed by Islamic State militants.
Both countries view IS -- which has seized vast swaths of territory in Iraq and Syria -- as a threat, but commentators say deep-seated mistrust keeps them from publicly cooperating to defeat the extremists.
A U.S. official said the two also discussed the prospects of reaching an agreement on reducing Tehran's atomic activities in exchange for an end to nuclear-related sanctions on the Tehran.
Their meeting came on the third day of the latest round of nuclear talks between Iran and six world powers -- the United States, Russia, China, Britain, France, and Germany.
The talks have been stalled for months over Iran's opposition to sharply reducing the size and output of centrifuges that can enrich uranium both to levels needed for reactor fuel or the core of nuclear warheads.
Iran denies Western charges it is using its nuclear program to secretly develop nuclear weapons.