Vienna - No agreement on the methodology for a probe of alleged Iranian nuclear weapons projects was achieved during two days of talks between Iran and UN nuclear officials this week, a UN nuclear inspector said Friday in Vienna.

"Differences remain," chief inspector Herman Nackaerts said when he returned to Vienna with International Atomic Energy Agency (IAEA) officials from the talks in Tehran.

Negotiations on granting UN nuclear experts access to suspect sites, experts and documents have gone on for a year.

During this time, the IAEA has also not been able to visit the key Parchin military site, where key nuclear weapons components were allegedly tested.

"Also on this occasion, no access was granted to Parchin," Nackaerts said.

A new round of talks was scheduled for February 12 in Tehran. Iran denies that it has worked on developing nuclear weapons and says that Western intelligence findings that form the basis of the IAEA's probe are fabricated.

One key stumbling block of the talks has been Iran's demand to get access to these intelligence documents.

The Iranian Foreign Affairs Ministry said Tuesday that the international nuclear watchdog must acknowledge Iran's right to develop nuclear power before it would be allowed to inspect the Parchin site.