An Iranian news agency said on Wednesday that Iran and six world powers would resume talks over the Islamic state's nuclear program in late January, but a European Union official said the two sides had yet to agree a date.
The Iranian Students' News Agency (ISNA) gave no source for its report and later on Wednesday appeared to have deleted it from its website, without giving a reason.
Russia voiced alarm last week at delays in agreeing a new round of talks on the Iranian program, which the West suspects is aimed at developing a nuclear weapon capability.
Iran says it is enriching uranium for peaceful energy purposes.
Three rounds of negotiations in 2012, the last one in June in Moscow, failed to achieve a breakthrough in the decade-old dispute which has the potential to spark a new Middle East war.
The ISNA report said the two sides would meet again on January 28 and 29. But it also said the date could change depending on which location was agreed upon. It cited Istanbul and Geneva and "some other cities'' as possible places.
A diplomat in Vienna, where the U.N. nuclear agency is based, suggested the dates cited by ISNA could be correct. Both the diplomat and ISNA said the venue had not yet been decided.
"That's what we've heard too, still working on the venue,'' the diplomat said.
But a spokesman for European Union foreign policy chief Catherine Ashton said in Brussels that no date had yet been set.
"Contacts are still ongoing. We are waiting for the Iranians to respond,'' Michael Mann said when asked about the ISNA report.
Ashton oversees contacts with Iran over its disputed nuclear program on behalf of the six powers - the United States, Russia, China, France, Britain and Germany.
Western diplomats had hoped for negotiations to restart in December or mid-January. Since the last meeting in June, Iran has pressed ahead with its disputed work and amassed more material which can have both civilian and military purposes.
Israel - a U.S. ally believed to have the Middle East's only nuclear arsenal - has threatened military action if diplomacy and economic sanctions intended to rein in Iran's uranium enrichment program do not resolve the stand-off.
Enriched uranium can fuel nuclear power plants, Iran's declared goal, but also provide material for bombs if refined further, which the West suspects is Tehran's ultimate ambition.
ISNA's report coincided with a new round of separate negotiations in Tehran on Wednesday between the U.N. nuclear agency and Iran.
The International Atomic Energy Agency (IAEA) has been trying for a year to negotiate a so-called structured approach with Tehran that would give it access to officials, documents and sites.