Iran's atomic chief Ali Akbar Salehi said on Friday that Tehran was ready to adopt "any confidence-building measure" on its atomic programme as it opens two nuclear facilities to foreign dignitaries.

Salehi's remarks came as Iran undertakes a two-day tour of its Natanz and Arak nuclear facilities from Saturday, and ahead of key talks with six world powers next week at Istanbul over Tehran's atomic drive.

"We are ready to adopt any confidence-building measure while preserving our nuclear rights," Salehi told ISNA news agency.

"We hope that mutual trust can be built (between Iran and the six world powers)," he said. "I think sooner or later logic should prevail in international affairs."

The six powers -- Britain, China, France, Russia, the United States and Germany -- suspect Tehran is masking a weapons drive under the guise of a civilian nuclear programme. Iran denies the charge.

Salehi reiterated that the proposed tour of its Natanz and Arak nuclear facilities was a confidence-building initiative.

"No country in the world will show its nuclear installations to others and this is a sign that Iran's nuclear activities are peaceful," said Salehi, who oversees Iran's nuclear programme.

Iran has also welcomed "nuclear experts" to join in the tour.

Iran said last week that invitations to visit the sites had been sent to some ambassadors whose nations are members of the International Atomic Energy Agency.

Iran's IAEA ambassador Ali Asghar Soltanieh told ISNA that "leaders and representatives of the Non-Aligned Movement... the ambassador and representative of the Arab league in international bodies in Vienna as well as the Syrian and Venezuelan ambassadors in the IAEA have expressed willingness to join."

Such visits are rare. The last trip that Tehran arranged for members of the IAEA was in February 2007.

Diplomatic sources at the IAEA, the UN nuclear watchdog in Vienna, said invitations had gone out to Russia, China, Egypt and Cuba as well as to Hungary, as rotating president of the European Union.

The EU said it would not attend.

The sources said the United States, Britain, France and Germany were not on the list.

Iran's allies Russia and China too have not given a categorical affirmation of whether their representatives would participate in the tour and Moscow even asked Tehran to explain some "grey areas" of its atomic programme.

The unusual move to open facilities comes as Tehran works to garner support for its atomic drive in the run-up to the Istanbul talks on January 21 and 22.

Salehi on Wednesday said that Iran will not discuss its "nuclear dossier" during the Istanbul talks.

But EU chief diplomat Catherine Ashton, who represents the six powers in negotiations with Iran, said on Thursday Tehran's nuclear controversy would figure in the talks.

"I'm very clear that we are coming to discuss the nuclear issue and that is what we will do," Ashton told reporters after meeting with Turkish Foreign Minister Ahmet Davutoglu in Istanbul.

"Our purpose in meeting is to now look for tangible credible ways to make a move forward" she added.