Global powers have asked Iran to meet in February to discuss its nuclear program.
Michael Mann, the spokesman for EU foreign policy chief Catherine Ashton, announced the offer on January 28 in Brussels.
"The E3+3, through High Representative Ashton, has since the end of December regularly been proposing to the Iranians that we get together for the next round of talks. Iran did not accept our offer to go to Istanbul on the 28th and 29th of January and so we have offered new dates in February," Mann said.
The E3+3 is composed of France, Germany, and Great Britain plus China, Russia, and the United States.
Mann also blamed Tehran for the lack of agreement on a date for a meeting.
"Any suggestions that the E3+3 has asked for a delay is, frankly, wrong. We have continued to offer dates since December. We are disappointed that the Iranians have not yet agreed to that sort of meeting," Mann said.
Earlier on January 28, Moscow called on global powers and Iran to agree on a venue for talks.
Russian Foreign Minister Sergei Lavrov spoke at a news conference in Moscow.
"We are ready to meet at any location as soon as possible. We believe the essence of our talks is far more important than the setting any particular location can offer, and we hope that common sense will prevail and we will stop behaving like little children," Lavrov said.
Iran on January 28 rejected any suggestion that it was holding up nuclear talks with the six world powers.
Foreign Minister Ali-Akbar Salehi told the Fars news agency that Iran wanted the talks to have momentum and achieve suitable results for both sides.
He also said that Kazakhstan, Sweden, Switzerland, and Turkmenistan had declared their willingness to host the nuclear talks.
The last round of negotiations between Iran and the six world powers ended without a breakthrough in Moscow in June.
At that time, Tehran rejected calls to curb its nuclear activities and demanded an end to sanctions.
Iran denies it is working on building a nuclear weapon, saying it only pursues nuclear energy.
Based on reporting by Interfax and Reuters