U.N. nuclear watchdog officials left Iran on Monday after talks with the head of its nuclear energy organization, the semi-official ISNA news agency reported, without saying whether they addressed an impasse over uranium traces at undeclared sites.
The issue has been an obstacle to progress in wider talks to revive Iran's 2015 nuclear deal with major powers, meant to curb its disputed uranium enrichment program in return for lifting sanctions imposed by Washington after exiting the pact in 2018.
Talks to restore the nuclear accord have been at a stalemate since September. Western powers accuse the Islamic Republic of raising unreasonable demands after all sides appeared to be nearing a deal.
The uphill climb to salvage the pact has grown steeper this year. Iran has brutally cracked down on street protests, Western states say Russia has used Iranian drones in its war in Ukraine, and Tehran has accelerated its nuclear program, all of which raise the political price to give Iran sanctions relief.
Iran has acknowledged that it supplied Moscow with drones but said they were sent before Russia's invasion of Ukraine.
Speaking at a conference in Tehran, Kamal Kharrazi, a senior adviser to Supreme Leader Ayatollah Ali Khamenei, said the issue of nuclear safeguards was the last one to resolve ahead of reviving the deal, the semi-official Tasnim news agency said.
"Iran is ready to return to its JCPOA (nuclear deal) obligations. Many problems have been resolved in the negotiations, now the only issue is safeguarding," it quoted Kharrazi as saying.
"We hope that this matter will be resolved during the visit of the (U.N. nuclear) agency's delegation to Tehran," he said.
The United States said in October that reviving deal was "not our focus right now" as Iran had shown little interest and that Washington was concentrating on how to support Iranian protesters - a view echoed by Germany in November.
ISNA said the delegation of the International Atomic Energy Agency, led by the IAEA's deputy director general for safeguards, Massimo Aparo, held negotiations with Iranian teams and met Mohammad Eslami, head of Iran's Atomic Energy Organization.
The two sides exchanged views on "future joint cooperation and programs, in addition to safeguarding issues", ISNA said.
Speaking last week, Eslami said he hoped the IAEA visit could help resolve outstanding issues between the two sides.
The IAEA said last year Iran had failed to explain traces of uranium found at several undeclared sites, which the agency said affected its ability to verify whether Iran's nuclear activity was part of a peaceful energy project, as Tehran has always maintained.
