(Bloomberg) -- World powers prepared to kick off their latest efforts to save the ailing 2015 nuclear deal with Iran in Vienna Monday, with rival diplomats far apart over how to rescue an accord that has major repercussions for Middle Eastern security and oil markets.

While there’s no expectation of any significant breakthroughs, the meeting will be the first attended by officials representing hardline Iranian President Ebrahim Raisi, elected in June.

Negotiations between Iran, the European Union, China and Russia will start at the historic Palais Coburg at 2 p.m. in the Austrian capital. The U.S., having all but collapsed the deal when the Trump administration exited three years ago, won’t be in the room but will take part indirectly through EU mediators.

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The Coburg is where the original accord was sealed in 2015 after almost three consecutive weeks of intense negotiations. On Monday, it was cordoned off by dozens of police and steel barricades, with nearby shops and restaurants remain closed with Austria entering its second week of a nationwide lockdown to stem the spread of Covid-19.

Iran has said the talks must secure full, guaranteed and verifiable removal of U.S. sanctions -- including on its critical oil exports -- and a commitment that Washington will never seek to leave a restored pact. The Biden administration has played down expectations of progress, pointing out it can’t bind the hands of successor governments and stressing deep concerns over the extent to which advances in Iran’s nuclear knowledge can be effectively unwound. 

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Iran’s top negotiator, Deputy Foreign Minister Ali Bagheri Kani, has said he will be using a translator in the talks, which is likely to slow the process. 

His delegation consists of some 40 people, the semi-official Khorrasan newspaper reported Sunday, including mid-ranking officials from the oil ministry and central bank. Iran’s OPEC governor, Amir Hossein Zamaninia, a fixture during earlier rounds of talks this year, won’t be part of the team.

In response to Trump’s sanctions, Iran significantly expanded its nuclear program by ramping up uranium enrichment to 60%, just below what’s needed to build a nuclear weapon. Iran has always denied a military dimension to its atomic program but western fears it would pursue a bomb drove diplomacy that culminated in the 2015 deal.

Tehran has also curtailed access for inspectors from the United Nations International Atomic Energy Agency to various sites and facilities.  

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