The head of the International Atomic Energy Agency (IAEA) is pressing Iran to grant his inspectors access "without further delay" to a military site where Iran is believed to conducting nuclear activities.
IAEA head Yukiya Amano told the governing board of the IAEA in Vienna on September 10 that "activities" at the Parchin facility -- a reference to suspected clean-up work there -- could have an "adverse impact" on the IAEA's investigation, if and when inspectors were allowed to go there.
"It is a matter of concern that activities which have taken place since February 2012, at the location within the Parchin site referred to in my report to the board, will have an adverse impact on our ability to undertake effective verification there," Amano said.
Amano said "no concrete results" had been achieved in meetings between senior IAEA officials and Iran since January.
Iran told the UN agency in a letter last month that the allegation of nuclear-linked work at Parchin, located southeast of Tehran, was "baseless."
Amano, speaking at the opening, said the lack of concrete results despite months of discussions between the UN nuclear agency and Iran was "frustrating."
"Despite the intensified dialogue between the agency and Iran since January 2012, no concrete results have been achieved so far," Amano said. "This is frustrating because, without Iran's full engagement, we will not be able to start the process to resolve all outstanding issues, including those concerning possible military dimensions to its nuclear program."
Iran's envoy to the IAEA, Ali Asghar Soltanieh, earlier told reporters that Tehran would "continue" to cooperate with the UN agency, but that the Islamic republic's national security must be taken into consideration.
Iran says its nuclear program is entirely peaceful and is aimed at producing electricity, not making bombs.
The 35-member IAEA board is expected to discuss Iran at a closed door meeting on September 12.
Diplomats say the United States and its Western allies are pushing for a resolution rebuking Iran for its lack of cooperation with the IAEA's investigation into its nuclear activities.
But it is unclear whether Russia and China -- who are part of a group of six world powers trying to find a diplomatic solution to the long-running dispute -- would agree to such a move.
Russia and China have criticized Western sanctions imposed against Iran. Russia last week said it saw no evidence Iran's nuclear program was aimed at making weapons.
Based on reporting by AFP and Reuters