Iran said Monday that all measures it has taken to roll back on its commitments under the 2015 nuclear deal with world powers are "reversible".

"If the agreement is finalised in Vienna tomorrow, all the measures carried out by Iran are technically reversible," Iran's foreign ministry spokesman Saeed Khatibzadeh told reporters.

Iran on Wednesday said it had disconnected some UN nuclear watchdog cameras monitoring its nuclear site.

The move came as a resolution was adopted by the International Atomic Energy Agency's Board of Governors censuring the Islamic republic for its lack of cooperation.

IAEA chief Rafael Grossi said Thursday his agency had been informed that 27 cameras were being removed, leaving about 40 still in place.

He warned that the move could deal a "fatal blow" to negotiations to revive the 2015 nuclear accord, stalled since March.

Iran meanwhile says the disconnected cameras were not part of a safeguards agreement with the IAEA.

Iran "is fully honouring its commitments under the safeguards agreement", Khatibzadeh said, adding that the country has only "stopped some of the voluntary measures".

"All of the safeguard cameras of the Islamic Republic of Iran are in place; all of the measures it has been undertaking under the supervision of the IAEA are in place," he added.

The talks in the Austrian capital, which began in April last year, aim to return the US to the nuclear deal, including through the lifting of sanctions on Iran, and to ensure Tehran's full compliance with its commitments under the agreement.

The deal known formally as the Joint Comprehensive Plan of Action (JCPOA) gave Iran sanctions relief in exchange for curbs on its nuclear programme to guarantee that it could not develop a nuclear weapon -- something Tehran has always denied wanting to do.

But the US unilaterally withdrew from the accord in 2018 and reimposed severe economic sanctions, prompting Iran to begin rolling back on its own commitments.

Khatibzadeh said the on-off dialogue in Vienna can yield results if the US "puts aside the delusion of using leverage" and "accepts to fully meet its commitments under the JCPOA and UN resolution 2231" which supports it.

"What we are focusing on is that this agreement becomes operational and is signed, and this is possible if the US changes its approach and manner," he added.

"Unfortunately the US is extending the talks and wants to resolve some bilateral issues through the Vienna negotiations, which is impossible."