An Iranian official has criticized the chief of the U.N. atomic agency for demanding snap inspections of Iran's nuclear sites, saying such a demand stands in the way of Tehran and world powers reaching a deal on the country's controversial nuclear program.

The so-called P5+1 group — Britain, China, France, Russia, the U.S. and Germany — face an end-of-the-month deadline to reach a final nuclear deal with Iran.

Iran's nuclear spokesman Behrouz Kamalvandi was quoted Tuesday on Iranian state TV's website as saying that snap inspections are "illegal." He did not elaborate.

Kamalvandi was responding to the demand earlier this month by Yukiya Amano, the head of the International Atomic Energy Agency, that Tehran agree to the inspections.

The IAEA suspects that Tehran has worked on nuclear arms in the past.