The UN nuclear watchdog said there had been "no progress" in talks with Tehran on disputes over the monitoring of Iran's atomic programme, just days before talks restart on reviving the 2015 Iran nuclear deal.
Rafael Grossi, director general of the International Atomic Energy Agency (IAEA), told a quarterly meeting of the agency's board that talks he held in Tehran on Tuesday were "inconclusive" despite being "constructive".
Grossi had sought to tackle constraints put on IAEA inspections earlier this year, outstanding questions over the presence of undeclared nuclear material at sites in Iran, and the treatment of IAEA staff in the country.
"In terms of the substance... we were not able to make progress," Grossi told reporters, saying that the lack of agreement had come "in spite of my best efforts".
Iran and the agency currently have a temporary agreement that gives the IAEA access to monitoring equipment at Iran's nuclear facilities, AFP reported.
However, the Agency has warned that the agreement is not a durable solution and Grossi said he was "close to... the point where I would not be able to guarantee continuity of knowledge" of Iran's nuclear programme if it continued.
Grossi also said he had raised concerns while in Tehran about security checks on IAEA inspectors which the agency has described as "excessively invasive".
He noted that the IAEA and Iran had a legal agreement "which is intended to protect inspectors from intimidation, from seizure of their property". "Our Iranian colleagues have instituted a number of measures which are simply incompatible" with this, he said.
