The meeting next Wednesday of the so-called E3+3 (Britain, China, France, Germany, Russia, the United States) and Iran comes as President Donald Trump is weighing whether to quit the historic 2015 agreement.
European Union foreign policy chief Federica Mogherini will chair the talks, held on the sidelines of the UN General Assembly meeting, diplomats said.
Iranian President Hassan Rouhani is expected to touch on the fate of the nuclear deal in his UN address on Wednesday, a day after Trump will deliver his first speech to the 193-nation assembly.
The US on Thursday waived nuclear-related sanctions on Iran but slapped new ones on 11 companies and individuals accused of engaging in cyber attacks against US banks.
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Trump is due to decide before October 15 whether Iran has breached the 2015 nuclear agreement, and critics fear he may abandon an accord they think prevents Tehran from building a nuclear bomb.
Under the nuclear deal, Iran surrendered much of its enriched uranium, dismantled a reactor and submitted nuclear sites to UN inspection, while Washington and Europe lifted some sanctions.
On a visit to the United States in July, Zarif complained that he had yet to discuss the agreement with Tillerson and that the administration was sending "contradictory signals" about the fate of the landmark agreement.
"There are no communications between myself and Secretary Tillerson," Zarif said.
"It doesn't mean there can't be. The possibilities for engagement... have always been open."
