The US is weighing whether the Iranian nuclear deal serves its security interests even as Iran says it does not expect it to abandon the agreement.
A collapse of the 2015 deal, which President Donald Trump has called "an embarrassment" but which is supported by the other major powers that negotiated it with Iran, could trigger a regional arms race and worsen Middle East tensions.
Iranian President Hassan Rouhani vowed his country would not be the first to violate the agreement under which Tehran agreed to restrict its nuclear program in return for the loosening of economic sanctions that had crippled its economy.
"We don't think Trump will walk out of the deal despite (his) rhetoric and propaganda," Rouhani told reporters on the sidelines of the UN General Assembly gathering of world leaders.
Trump told reporters he had made a decision on what to do about the agreement but would not say what he had decided.
Matters were no clearer after Iran and the world powers that negotiated the deal - Britain, China, France, Germany, Russia and the US - met for talks that a European source said included a long discussion between the US and Iranian foreign ministers.
It was the first time the two men, US Secretary of State Rex Tillerson and Iranian Foreign Minister Mohammad Javad Zarif, had met since Trump took office.
The EU's foreign policy chief, Federica Mogherini, said all sides believed there had been no violations to the deal but she was unable to say after the meeting whether the US would stick to it.
Tillerson told reporters Trump did not wish to leave the Iran nuclear issue to the next president.
Trump must decide by October 15 whether to certify that Iran is complying with the pact.
If he does not, Congress has 60 days to decide whether to reimpose sanctions.