By Michelle Moghtader and Fredrik Dahl
DUBAI/VIENNA (Reuters) - Iran held serious discussions with the U.N. nuclear watchdog on Sunday about issues that are part of an investigation into suspicions Tehran has conducted atomic bomb research, official media reported on Monday.
Iran's envoy to the International Atomic Energy Agency, Reza Najafi, appeared to acknowledge, however, that Tehran had not fully implemented five transparency measures by an Aug. 25 deadline, as agreed with the IAEA in May.
"Iran is in the process of implementing the five agreed steps," the official IRNA news agency quoted him as saying.
Diplomats in Vienna last week told Reuters that Iran had apparently failed to meet the target date for answering IAEA questions about its nuclear program, but that contacts between the two sides were continuing.
Western officials say Iran must address the IAEA's concerns and that this is vital for any chance of success in parallel negotiations to end a decade-old nuclear standoff with the West.
Iran's Press TV website said Iranian and IAEA experts met in Tehran on Sunday. Najafi said they exchanged information and that the discussions were "serious", IRNA reported, adding they would continue and be followed up soon.
There was no immediate comment from the IAEA, a Vienna-based U.N. agency which for years has been investigating intelligence suggesting Iran has carried out experiments and other activities that could be used for developing nuclear weapons.
Iran says its nuclear program is entirely peaceful, but Western countries fear Tehran's real aim is to develop weapons capability and have imposed economic sanctions in an effort to force the Islamic Republic to curb its atomic work.
As part of an Iran-IAEA cooperation accord reached in November in an attempt to revive the agency's long-stalled investigation, Tehran agreed in May to carry out five specific steps by late August to help allay international concerns.
They included providing information on alleged experiments on explosives that could be used for an atomic device, and studies related to calculating nuclear explosive yields.
While denying such information as baseless and fabricated, Iran has promised to cooperate with the IAEA since Hassan Rouhani, seen as a pragmatist, was elected president in 2013.
"Three out of the five steps have been completely implemented," Najafi said, without giving details.
Apart from information related to the IAEA's investigation, Iran also agreed to give it access to sites including a centrifuge research and development facility by late August.
In 2011, the IAEA published a report that included intelligence indicating Iran had a nuclear weapons research program that was halted in 2003 when it came under increased international pressure. The intelligence suggested some activities may later have resumed.
After years of what the West saw as Iranian stonewalling, Iran as a first step in May gave the IAEA information about why it was developing "bridge wire" detonators, which can be used to set off atomic explosive devices. Iran says they are for civilian use, and wants this topic in the investigation closed.
In mid-July, the separate negotiations on a diplomatic settlement between Iran and the United States, France, Germany, Britain, China and Russia, were extended until late November.
(Editing by Robin Pomeroy)