Nuclear talks (archive)
Nuclear talks (archive) Reuters

Major world powers and Iran will hold fresh talks in Vienna on April 22 and 23 to build on the framework accord reached on Tehran's nuclear program, the European Union (EU) announced Thursday, according to the AFP news agency.

The two sides "will continue work towards a comprehensive solution to the Iranian nuclear issue based on the key understandings reached in Switzerland on April 2," an EU statement said.

The talks will take place at political director level, involving first Helga Schmid of the EU's external affairs arm and Iranian Deputy Foreign Minister Abbas Araqchi.

They will then be joined by officials from the five UN Security Council members -- Britain, China, France, Russia and the United States plus Germany.

"In parallel, experts will continue the work on the technical details necessary to finalise the political work," the statement said.

Marathon talks in Lausanne last month ran overtime but finally produced a framework political agreement whereby Iran would accept strict controls over its nuclear program in return for the easing of damaging economic sanctions.

The restrictions are meant to prevent Iran from acquiring a nuclear weapon, as feared in the West, although Tehran insists its program is purely for civilian use.

The sides now have until June 30 to reach a final accord but they will have to crack some of the toughest issues -- the lifting of global sanctions and a mechanism to reintroduce them if Iran reneges on the deal, as well as research and development and the possible military dimensions of the Iranian program.

The issue of how and when sanctions are to be removed is one of many contradictions between the United States and Iranian versions of the deal.

Another point of contention is that the U.S. has said Iran will stop using advanced centrifuges and limit itself to researching them, while top Iranian officials last week said they will start using advanced IR-8 centrifuges that are 20-times as effective as standard ones as soon as a deal is reached, meaning they would be able to produce a nuclear arsenal in a rapid timeframe.

For his part, U.S President Barack Obama admitted in an interview last week that as a result of the deal, Iran will be able to reach a "zero" breakout time by 2028, meaning it could produce nuclear weapons immediately whenever it wanted to.

On Wednesday, Iranian President Hassan Rouhani reiterated his stance that Tehran will not sign on to any final deal unless all economic sanctions are completely lifted, saying, "If there is no end to sanctions, there will be no deal."