The European Union says it is up to the International Atomic Energy Agency (IAEA) to visit Iran's nuclear sites.
An EU spokesman said Wednesday the bloc has not responded to Iran's invitation to have select foreign diplomats tour its nuclear facilities.
Tehran has suggested the visit take place on January 15 and 16, ahead of talks on Iran's nuclear program in Istanbul later this month. The invitation excluded key world powers who will attend the meeting, including the United States, France, Britain and Germany.
The gathering will include representatives from Iran and the P5+1, the five permanent members of the U.N. Security Council plus Germany.
Diplomats say Iran only invited two of the P5+1 members - Russia and China. They say Tehran also invited Egypt, Turkey, Brazil, Cuba and Hungary, which currently holds the EU presidency.
Western countries, including the United States, believe Iran is secretly trying to develop nuclear weapons. Iran says its nuclear program is for peaceful means.
The U.N. Security Council has imposed four sets of sanctions on Iran for its refusal to suspend sensitive nuclear work. The European Union, the United States and other nations have also imposed economic sanctions on Tehran.
Some information for this report was provided by AP, AFP and Reuters.