Access to an Iranian nuclear site 25 miles northwest of Tehran, which was allegedly targeted by saboteurs in June, has become a bone of contention between Iran and the West.
Iran has rejected the latest report by the International Atomic Energy Agency (IAEA), which accuses Iran of failing to honor the deal struck with the watchdog two weeks ago.
Calling the report "biased" and "inaccurate", Behrouz Kamalvandi, a spokesman for Iran's nuclear agency, said the IAEA should not disrupt the "constructive process".
Earlier this month, Iran allowed the UN nuclear watchdog to "service" the surveillance cameras installed at its nuclear sites in a bid to ease concerns over Iran's nuclear activities.
The announcement came during the IAEA chief Rafael Grossi's visit to Tehran, during which he held talks with the newly-appointed head of Iran's nuclear agency Mohammad Eslami.
On Sunday, the IAEA said Iran has "failed to fully honor" the terms of the deal reached on Sept. 12. It allowed the agency to replace memory cards in most of the equipment, but refused access to a workshop that makes centrifuge components at the TESA Karaj complex in west Tehran, the agency said.
"The (IAEA) Director General (Rafael Grossi) stresses that Iran's decision not to allow Agency access to the TESA Karaj centrifuge component manufacturing workshop is contrary to the agreed terms of the Joint Statement issued on 12 September," the IAEA said in a statement.
Reacting strongly, Kamalvandi said the joint statement did not cover the surveillance equipment of the Karaj complex, which he said is still under" security investigation".
The complex, which belongs to the Atomic Energy Organization of Iran (AEOI), faced a sabotage attempt on June 23, causing some damage. Iran blamed Israel for it.
Kamalvandi said the request for UN inspectors' access to the Karaj complex was raised during Grossi's visit to Tehran earlier this month and again on the sidelines of the meetings of the IAEA general assembly in Vienna.
He called on the UN nuclear agency to "avoid wilful political stances" and "not to destroy the constructive processes" created in recent meetings between the two sides.
On Sunday, Iran's envoy to the UN nuclear agency, Kazem Gharibabadi, said the joint statement between Iran and the IAEA was achieved "due to Iran’s goodwill" to replace the storage media of the “identified equipment”.
"During the discussions in Tehran & Vienna, Iran indicated that since Tessa Karaj Complex is still under security and judicial investigations, equipment related to this complex are not included for servicing. That's why the phrase ‘identified equipment’ has been used in the joint statement," he said in a statement posted on Twitter.
Gharibabadi termed Grossi's report "inaccurate", which he said "goes beyond the agreed terms" of the joint statement.
"Any decision taken by Iran on monitoring equipment is only based on political rather than legal considerations and the Agency cannot and should not consider it as one of its entitlements," he said.
Iran's refusal to grant IAEA inspectors access to the site has prompted strong protests from the US and European countries.
In a statement to a meeting of the IAEA board on Monday, Washington said Iran must grant the UN nuclear watchdog access to the workshop at the TESA Karaj complex to re-install cameras or "face diplomatic action" by the watchdog's board of governors.
"We call on Iran to provide the IAEA with needed access without further delay," the statement said. "If Iran fails to do so, we will be closely consulting with other Board Members in the coming days on an appropriate response."
The European Union countries also urged Tehran to provide IAEA inspectors access to the nuclear site in western Tehran.
The dispute comes amidst heightened tensions between Iran and the West, with efforts to revive the 2015 nuclear deal stalled.