Senior U.S. officials say President Barack Obama and Iranian President Hasan Rouhani will not meet while both leaders are at the United Nations.
The officials say a meeting proved to be too complicated for the Iranians. But they say work is under way at the staff level to resolve an impasse over Iran's nuclear program.
U.S. and Iranian leaders have not met in 36 years.
The officials insisted on anonymity because they were not authorized to discuss the decision publicly.