Iran on Monday denied it is sanitising a suspect military base where the UN atomic watchdog wants to probe evidence of possible weapons research.
"Clean-up of such places is not possible," Foreign Minister Ali Akbar Salehi told AFP.
His remarks came a day after International Atomic Energy Agency (IAEA) chief Yukiya Amano said in Baghdad possible efforts to dismantle traces of possible weapons research at the Parchin site near Tehran were "ongoing."
"Yes, the activities at Parchin are ongoing, but I am not in a position to discuss the details today," Amano told reporters.
Salehi rejected the remarks.
"These words have no technical basis -- if he has actually made such remarks," Salehi said.
Western nations have accused Iran of removing evidence of past suspected weapons research activities at Parchin.
The IAEA wants Iran to grant access to the site, which it visited twice in 2005 but wants to examine again.
Iranian officials have previously emphasised that Parchin is an off-limits military base and that the IAEA's focus on it is overblown and based on "false" Western intelligence.
Since the summer, some buildings at the base have been covered in massive tarpaulins to prevent surveillance by Western satellites.
Western and other governments suspect Iran has been trying to develop a nuclear weapons break-out capability. Tehran denies any such ambition, insisting its nuclear programme is exclusively for power generation and medical purposes.