VIENNA -- Iran on Saturday gave the UN nuclear agency documents linked to the agency's probe of allegations that Tehran tried to develop atomic arms, along with a confidential explanation that is unlikely to veer from previous Iranian denials of work on such weapons.

Announced by the UN's International Atomic Energy Agency, the handover meets a key deadline Iran has committed to as part of its overarching deal with six world powers promising Tehran sanctions relief in exchange for nuclear concessions.

The July 14 deal's main focus is curbing Iran's present nuclear program that could be used to make weapons. But a subsidiary element obligates Tehran to co-operate with the IAEA in its probe of the allegations.

The investigation has been essentially deadlocked for years with Tehran asserting the allegations are based on false intelligence from the U.S., Israel and other adversaries. But Iran and the UN agency agreed last month to wrap up the investigation by December, when the IAEA plans to issue a final assessment on the allegations. Saturday was the target date for Tehran to provide the agency documents related to the probe and its version of what they mean.

Both Iran and the IAEA were upbeat when announcing the agreement last month. But Western diplomats from IAEA member nations who are familiar with the probe are doubtful that Tehran will diverge from claiming that all its nuclear activities are -- and were -- peaceful, despite what they say is evidence to the contrary.

They say the agency will be able to report in December. But that assessment is unlikely to be unequivocal because chances are slim that Iran will present all the evidence the agency wants or give it the total freedom of movement it needs to follow up the allegations.

Still, the report is expected to be approved by the IAEA's board, which includes the United States and other powerful nations that negotiated the July 14 agreement. They do not want to upend their July 14 deal, and will see the December report as closing the books on the issue.