The Iranian ambassador to the International Atomic Energy Agency (IAEA), Ali Asghar Soltanieh, denied reports that a team from the UN nuclear watchdog was blocked from visiting its nuclear sites.

A senior IAEA team visited Iran but said it was prevented from seeing nuclear facilities, increasing speculation that Iran is using its uranium enrichment programme to build nuclear weapons.

"It is disappointing that Iran did not accept our request to visit Parchin [military plant] during the first or second meetings," IAEA director general Yukiya Amano said after the visit.

"We engaged in a constructive spirit, but no agreement was reached."

Soltanieh refuted the IAEA's claims.

"After the second round of talks, we agreed to the IAEA visiting the facilities, where it was alleged that strong explosive materials had been tested, but the agency's delegation returned to Vienna without paying a visit to the nuclear sites, " the Iranian Students News Agencyquoted him saying.

Iranian foreign minister Ali Akbar Salehi called for more talks with the agency at the UN-sponsored Conference on Disarmament in Geneva.

"There was some disagreement on drafting an initial framework that would set the ground for a new road map as how to proceed," Salehi said. He was optimisitc, however, that talks would go ahead.

At the conference, the foreign minister insisted that Iran's nuclear programme was for peaceful purposes only, saying possessing or producing nuclear weapons was a great "sin".