Atomic energy organisation spokesman Behrouz Kamalvandi will hold a news conference to set out the details of Iran's third cut to its nuclear commitments since May, ISNA said on Thursday.

President Hassan Rouhani said Wednesday that the new steps included abandoning all limits set by the 2015 deal to Iran's nuclear research and development.

He spoke of "expansions in the field of research and development, centrifuges, different types of new centrifuges, and whatever we need for enrichment," but did not elaborate.

Iran and three European countries -- Britain, France and Germany -- have been engaged in talks to try to save the nuclear deal that has been unravelling since US President Donald Trump withdrew from it in May last year and unilaterally reimposed sanctions.

Iran has expressed mounting frustration at Europe's failure to offset the effect of renewed US sanctions in return for its continued compliance with the agreement.

It had already hit back twice with countermeasures in response to the US withdrawal from the deal.

On July 1, Iran said it had increased its stockpile of enriched uranium to beyond the 300-kilogram maximum set by the agreement.

A week later, it announced it had exceeded a 3.67-percent cap on the purity of its uranium stocks.

The UN's nuclear watchdog, the International Atomic Energy Agency, said on August 30 that Iran's uranium stockpile stood at about 360 kilograms and that just over 10 percent of it was enriched to 4.5 percent.

Rouhani has stessed that the countermeasures Iran has adopted are all readily reversible if the remaining parties to the deal honour their undertakings to provide sanctions relief.

The EU urged Iran on Thursday to reverse its scale-back of its commitments.

"These activities we consider are inconsistent with the JCPOA (the nuclear accord). And in this context we urge Iran to reverse these steps and refrain from further measures that undermine the nuclear deal," European Commission spokesman Carlos Martin Ruiz de Gordejuela said.

A senior US official on Wednesday ruled out any exemptions from Iran sanctions to permit a French-proposed credit line, which Tehran says could bring it back to full compliance with the nuclear deal.

"We can't make it any more clear that we are committed to this campaign of maximum pressure and we are not looking to grant any exceptions or waivers," Brian Hook, the State Department coordinator on Iran, told reporters.