Volker Stanzel, political director in the German foreign ministry, issued a statement urging Iran to talk after he chaired a meeting with his counterparts from Russia, China, the United States, France and Britain on Tehran's nuclear programme.
The West suspects Iran is pursuing the means to produce atomic bombs under cover of a civilian nuclear fuel programme. Iran denies the charge and says it only wants electricity from nuclear power.
"Iran should be aware of the urgent need to restore confidence in the exclusively peaceful nature of its nuclear programme through full cooperation with the international community," Stanzel said on behalf of the six powers.
His statement was a response to remarks by Iran's chief nuclear negotiator, Saeed Jalili, who was quoted by Iranian state television on Tuesday as saying Tehran was ready to talk to world powers.
"With reference to Dr Jalili's statement this week that Iran is ready to resume talks, I expect Iran to respond to the offer of talks (made) in April by agreeing to meet before (the) UNGA (U.N. General Assembly)," Stanzel said.
The U.N. General Assembly meeting is on Sept. 23-25.
A senior European official said the world powers were expressing a desire for a meeting, rather than a concrete expectation that one would take place.
The official said the powers wanted a meeting with the Iranians within two weeks and that there was disappointment that there had been no movement on the issue since April.
Jalili was also quoted on Tuesday as saying Iran had prepared an updated nuclear proposal, but the European Union foreign policy chief, Javier Solana, said on Wednesday he was still waiting for Iran to hand it over.
Sanctions Threat
U.S. President Barack Obama has given Iran until later this month to take up a six-power offer of talks on trade benefits if it shelves nuclear fuel production, or face wider sanctions that could target Iran's vulnerable gasoline sector.
Last week, the International Atomic Energy Agency (IAEA) said Iran had slowed its expansion of uranium enrichment and met some demands for transparency but allegations it researched how to build atom bombs look credible and Tehran must address them.
Russia and China, close trade partners of Tehran, may resist expected calls from Western powers to squeeze Iran's lifeblood oil sector by pointing to new Iranian gestures of cooperation with IAEA inspectors, as cited in the agency report.
A Western diplomat said it was unclear how Russia and China have reacted to the IAEA report last week.
"At the moment they're (Russia and China) looking pretty cautious," the diplomat said, adding that Moscow and Beijing might prefer to wait and see what is in Tehran's counterproposal before moving ahead with discussions on a possible four round of U.N. sanctions.
On Monday, German Chancellor Angela Merkel said Iran should realise how "very serious" this month's deadline is for negotiations on its nuclear programme.
However, IAEA Director-General Mohamed ElBaradei said in an interview released late on Tuesday that Iran is not going to produce a nuclear weapon any time soon and the threat posed by its atomic programme has been exaggerated.
"In many ways, I think the threat has been hyped," he told the specialist Bulletin of the Atomic Scientists.
