The UN nuclear watchdog has not yet given good enough reasons to visit an Iranian site where it suspects there may have been experiments for developing nuclear weapons, Reuters reported citing Iranian media.

The Parchin complex is at the centre of Western suspicions that Iran is developing atom bombs despite Tehran's repeated denials of any such ambition. A report from the International Atomic Energy Agency (IAEA) last week said satellite images showed "extensive activities" at Parchin.

Iranian officials have refused access to the complex, southeast of Tehran, saying it is a military site.

"The reasons and document have still not been presented by the agency to convince us to give permission for this visit," the head of the Atomic Energy Organization of Iran, Fereydoun Abbasi-Davani, was quoted as saying by Fars news agency on Saturday.

Six world powers failed to convince Iran last week to halt its most sensitive nuclear work, but they will meet again in Moscow next month to try to end a standoff that has raised fears of a new war that could threaten global oil supplies.

Last November, an IAEA report found that Iran had built a large containment vessel in 2000 at Parchin in which to conduct tests that the agency said were "strong indicators of possible weapon development."

In last week's report, the IAEA did not elaborate on what activities it believed were happening there, but Western diplomats suspect Iran is trying to remove any potentially incriminating evidence. Tehran rejects this charge.

After a visit to Tehran last week, IAEA chief Yukiya Amano said he was close to an agreement with Iran on inspection visits to nuclear facilities but some differences remained.