The National - The European Union on Thursday demanded that Iran U-turns on its watering down of commitments under the landmark nuclear deal signed with world powers in 2015 after Tehran said it would end curbs on atomic research.

On Saturday, Iran will announce details of its latest move to breach the clauses of the agreement in reaction to crippling sanctions imposed by US President Donald Trump.

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. In a televised address, Mr Rouhani said Iran from Friday will begin developing centrifuges to speed up the enrichment of uranium, which can produce fuel for power plants or for atomic bombs, as the next step in reducing its nuclear commitments.

Under the accord, Iran was allowed to keep restricted quantities of first-generation centrifuges at two nuclear plants. The successful development of more advanced centrifuges would enable it to produce material for a potential nuclear bomb several times faster.

"The atomic energy organisation (of Iran) is ordered to immediately start whatever is needed in the field of research and development, and abandon all the commitments that were in place regarding research and development," said Rouhani, without elaborating.

European Commission spokesman Carlos Martin Ruiz de Gordejuela told a media briefing in Brussels that the decision was "inconsistent" with the Joint Comprehensive Plan of Action, under which the accord is implemented.

"And in this context we urge Iran to reverse these steps and refrain from further measures that undermine the nuclear deal," he said.

The remaining powers signed to the agreement - Britain, France, Germany, Russia and China - are seeking to keep the deal alive. The European powers are trying to reduce US-Iran tensions, but Washington and Tehran are hardening their strategies.

In July, Iran abandoned commitments restricting its uranium stockpile and the level of uranium enrichment.

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

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

Iran has said that a French offer of a $15 billion credit line could bring it back to full compliance with the deal.

But a senior US official on Wednesday ruled out any sanctions exemptions that would permit a French-proposed credit line, which Tehran says could bring it back to full compliance with the 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.

Iran's Foreign Minister Mohammad Javad Zarif responded by tweeting that the US Treasury was "nothing more than a JAIL WARDEN."

"Ask for reprieve (waiver), get thrown in solitary for the audacity. Ask again and you might end up in the gallows," he tweeted.

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

The Iranian president on Wednesday gave Europe a 60-day ultimatum before Iran drops another commitment.

The US admitted on Wednesday that Mr Hook personally offered several million dollars to the Indian captain of an Iranian oil tanker suspected of heading to Syria.

The Financial Times reported that the State Department’s pointman on Iran sent emails to captain Akhilesh Kumar in which he offered "good news" of millions in US cash to live comfortably if he steered the Adrian Darya 1 to a country where it could be seized.

"We have seen the Financial Times article and can confirm that the details are accurate," a State Department spokeswoman said.

"We have conducted extensive outreach to several ship captains as well as shipping companies warning them of the consequences of providing support to a foreign terrorist organization," she said, referring to Iran's elite Revolutionary Guards.