Senior U.N. nuclear inspectors plan another trip to Iran soon after holding what both sides described as good talks on the Islamic state's disputed atomic programme.
The talks were a rare direct dialogue in the international stand-off, which has worsened in recent weeks as the West pursues a punitive embargo on Iranian oil and Tehran threatens retaliation.
Tehran says its uranium enrichment programme is solely for peaceful electricity generation and has dismissed allegations that it is seeking to develop nuclear weapons as baseless.
Led by the International Atomic Energy Agency's global head of inspections, the IAEA team returned on Wednesday from three days of talks in Iran to try to end three years of deadlock in efforts to resolve the questions about Tehran's nuclear work.
The fact both sides said talks would resume hinted that the round just completed at least created some basis for progress.
We are committed to resolve all the outstanding issues and the Iranians said they are committed too, Herman Nackaerts, IAEA deputy director general, told reporters after returning from Tehran.
But of course there is still a lot of work to be done and so we have planned another trip in the very near future.
Asked if he was satisfied with the talks, Nackaerts said: Yeah, we had a good trip.
He described the talks as intensive discussions with their Iranian counterparts but declined to give any more details, saying he first needed to brief his boss.
Western diplomats based in Vienna, the IAEA's headquarters, said the jury was still out on whether the mission accomplished anything concrete.
This visit will be judged by whether the Iranians provided the visiting IAEA team with cooperation on substantive issues. Anything short of that type of cooperation is not acceptable, one envoy said.
Another diplomat said the trip at least did not appear to have been a disaster and the door is still open.
Proliferation expert Mark Fitzpatrick described Nackaerts' statement about more meetings as a positive sign.
The IAEA would not be scheduling another trip unless they had an expectation of progress in clearing away at least some of the questions about suspicious past nuclear activity, said Fitzpatrick, a director of the International Institute for Strategic Studies.
In Tehran, Iranian Foreign Minister Ali Akbar Salehi also said more talks would be needed but did not say when.
We had very good meetings and we planned to continue these negotiations. The team had some questions about the claimed studies. One step has been taken forward, he told the semi- official Fars news agency in Tehran.
IAEA BOARD MEETING
By studies, Salehi was alluding to intelligence reports indicating that Iran has covertly researched ways to design a nuclear weapon - Western allegations that were backed up by a detailed IAEA report in November.
Salehi added: We were ready to show them our nuclear facilities, but they didn't ask for it.
Lower-level IAEA inspectors based in Iran have regular, if limited, access to Iran's declared nuclear installations.
Iran's chief nuclear negotiator, Saeed Jalili, had already announced Iran's readiness to hold talks with world powers.
I hope this meeting takes place in the not too distant future, Salehi said.
Western diplomats have often accused Iran of using offers of dialogue as a stalling tactic while it presses ahead with stockpiling enriched uranium, the key energy source in nuclear power plants or bombs, depending on the level of refinement.
They say they doubt whether Tehran will show the kind of concrete cooperation the IAEA wants.
The IAEA made clear before the visit it wanted to focus on its growing concerns of possible military dimensions to Iran's nuclear programme. Among others, its team included French nuclear weapons expert Jacques Baute, one diplomat said.
Olli Heinonen, Nackaerts' predecessor at the IAEA, said it would take time to resolve all outstanding issues but that coming weeks would show whether Iran was ready to take pragmatic steps to address international concerns.
It is of great importance that the IAEA experts will have unfettered access to information, sites, equipment and people, who have been involved in the military-related activities, Heinonen, now at Harvard University, said.
Friction between Iran and the West has worsened this year after the United States and the European Union imposed sanctions targeting Tehran's oil sector over its continued defiance of U.N. resolutions demanding it suspend enrichment, grant unfettered access to the IAEA and engage in negotiations.
Iran has been open to resuming talks with six world powers frozen for over a year but only to discuss broader international issues, not its nuclear programme.
The new Western measures take direct aim at the ability of OPEC's second-biggest oil exporter to sell its crude. Iran has threatened to cut off oil exports to EU countries before July 1, when the sanctions would take full effect.
U.S. intelligence chiefs told legislators in testimony on Tuesday that Iran is feeling the bite from sanctions and that its nuclear programme is now capable of yielding a weapon although Tehran had not yet decided on such a course.
(Additional reporting by Fredrik Dahl in Vienna, Tabassum Zakaria in Washington and Ramin Mostafavi in Tehran; Editing by Mark Heinrich)