"The foreign ministers of the P5+1 (Britain, China, France, Russia and the United States plus Germany) will travel to Vienna this week, probably Friday, Saturday and Sunday, but that does not mean we have reached an agreement," the official IRNA news agency quoted the diplomat as saying.
"They come to help find an agreement and then return to their countries and negotiations will continue," said the diplomat, who was not identified.
A final round of negotiations aimed at guaranteeing the peaceful nature of Iran's nuclear programme was launched in Vienna on Thursday, and the talks could stretch up to their July 20 deadline.
Tehran hopes to preserve its uranium enrichment programme on an industrial scale in order to produce the fuel for future nuclear power plants.
Iran's supreme leader Ayatollah Ali Khamenei said yesterday that Iran should eventually have a capacity to enrich uranium needed to produce enough fuel for its Bushehr reactor, which goes well beyond that Westerners could accept.