Rafael Grossi, head of the International Atomic Energy Agency (IAEA), said on Wednesday that he hoped a planned visit to Tehran as part of a probe into uranium traces found in Iran would still take place, AFP reported.
His comments came after Tehran had appeared to question a visit was even on the agenda.
The IAEA has long been pressing Iran to provide answers on the presence of undeclared nuclear material found at three sites.
A recent report by the agency concluded there had been "no progress" in the long-standing probe, which has been a key sticking point that led to a resolution criticizing Tehran in June.
"Maybe it is lost in translation," Grossi told reporters in Vienna on Wednesday. "But we hope that this technical meeting" aimed at resolving outstanding issues will happen.
"Some doubt" was now hanging over the visit by senior agency officials, Grossi said, but he added that he was hopeful Iran would be able to "clarify" that.
On Tuesday, the United States, Britain, France and Germany submitted another motion to the IAEA board censuring Iran over its lack of cooperation with the agency.
The Islamic Republic denounced the previous motion passed in June as "political" and responded to it by removing surveillance cameras and other equipment from its nuclear facilities.
The resolution comes as the talks on a revival of the 2015 deal remain stalled.
Iran in September announced it had submitted its comments to the US response to the European Union’s draft for reviving the 2015 Iran nuclear deal.
While Iran’s Foreign Ministry spokesperson said at the time that Iran’s response was prepared based on a constructive approach, a senior Biden administration official said the Iranian response "is not at all encouraging.”
A US official later said that the efforts to revive the 2015 Iran nuclear deal have “hit a wall” because of Iran's insistence on the closure of the UN nuclear watchdog's investigations.
On Monday, the US envoy for Iran, Robert Malley, said Iran's crackdown on protesters and the sale of drones to Russia have turned the United States' focus away from reviving the nuclear deal.
Speaking to reporters in Paris, Malley insisted that the United States would leave the door open to resume diplomacy "when and if" the time came, but stated that for now Washington would continue a policy of sanctions and pressure.