Vienna - The UN atomic watchdog's board on Tuesday drew a line under a long-running probe into Iran's past efforts to develop nuclear weapons, removing an important obstacle to implementing July's landmark deal with big powers, diplomats said.
A resolution approved by the International Atomic Energy Agency's 35-nation board of governors said the investigation was "implemented in accordance with the agreed schedule" and that this "closes the board's consideration of the matter".
Iran had warned that unless this happened, it would not implement key parts of July's accord with six major powers to scale down its nuclear programme in exchange for sanctions relief.
The IAEA keeps close tabs on Iran's nuclear programme, and its inspections role is set to grow under July's hard-fought deal, which defused a stand-off dating back to 2002.
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But the Vienna-based watchdog has also long sought to clear up allegations that until 2003, and possibly since, Iran also secretly sought to develop an actual nuclear weapon.
After stalling for many years, Iran agreed in July to co-operate with the IAEA to address the claims, which it has always rejected, allowing inspectors to visit sites and providing additional information.
As a result the IAEA on December 2 released a "final assessment" - even though it did not receive all the information it sought - concluding that some of the allegations were indeed accurate.
It said Iran conducted "a range of activities relevant to the development" of a nuclear bomb before the end of 2003 in a "co-ordinated effort", and that some activities continued until 2009.
It stressed though that these "did not advance beyond feasibility and scientific studies" and that there was no evidence that Iran diverted nuclear material such as uranium or plutonium to these efforts.
But despite the findings, the six major powers - the United States, Russia, China, Britain, France and Germany, who co-authored the IAEA resolution - have decided to move on.
Despite Iran's "long history of concealment, denial and deception", the July deal is "forward-looking", the US ambassador to the IAEA, Henry Ensher, said on Tuesday.
The powers stress that Iran will remain under close IAEA scrutiny to ensure that it does not contravene the July deal or again secretly engage in more research on getting the bomb.
Nor is Iran completely out of the woods with the IAEA, with the agency's "broader conclusion" that all Iran's activities are exclusively peaceful still to come.
This could take several more years, and Tuesday's resolution stated that the board will "remain seized" on the matter for another 10 years, or until the "broader conclusion", whichever is sooner.
The IAEA will also have to confirm that Iran has enacted all its commitments under the July deal - on a day to be dubbed "Implementation Day" - which is expected to happen in early 2016.
Under the deal Iran has pledged to slash the number of centrifuges - which "enrich" uranium for peaceful uses but also for a bomb - from around 19 000 to 6 104, of which 5 060 will still enrich.
Iran also has to change the design of a new nuclear reactor being built at Arak so that it produces substantially less plutonium, the alternative to uranium in a nuclear weapon.
By "Implementation Day" the Arak reactor core has to have been made inoperable by filling the openings with concrete.
Plus, Iran must reduce its stock of low-enriched uranium from several tons to just 300kg. Iran is expected to ship this material to Russia.
The last IAEA update on November 18 said that Iran had removed some 4 500 centrifuges. However, there was no progress at Arak or on the uranium stock.