"It's a reality. The IAEA (International Atomic Energy Agency) doesn't deal with Iran as it should," Behrouz Kamalvandi, spokesman of the Atomic Energy Organization of Iran, told state television late Thursday.

He argued that organisations such as the IAEA were "under the influence of powerful countries" which "finance them and in exchange apply pressure on them".

In a phone call on Friday with EU diplomatic chief Josep Borrel, Iran's Foreign Minister Hossein Amir-Abdollahian said it would be "possible to reach a favourable agreement" if sanctions are lifted.

"We will participate in the Vienna talks in good faith and seriously," he said, while calling for "a serious and sufficient guarantee" that the United States will not leave the nuclear deal.

After a mission to Tehran this week, IAEA head Rafael Grossi said his talks with Iranian officials had been "constructive" but "inconclusive".

"In terms of the substance... we were not able to make progress," Grossi told reporters in Vienna where the IAEA is based.

Kamalvandi said the Islamic republic was "trying to stand up for its rights and to counter the negative image that they (the international community) are trying to fabricate about us".

Western countries "say we are seeking a nuclear weapon and that we must be prevented at all costs", he said.

"The nuclear industry is an essential industry and one to which we are committed. Above all, we must not give up but instead pursue our efforts," the spokesman said.

Grossi's visit came ahead of the scheduled resumption on Monday of negotiations between Tehran and world powers aimed at reviving the 2015 nuclear deal that gave Iran sanctions relief in return for curbs on its nuclear programme.

The deal has been gradually disintegrating since former US president Donald Trump unilaterally withdrew from the accord in 2018.

President Joe Biden's administration, however, says it is working to return the United States to the accord whose other parties are Britain, China, France, Germany and Russia.