The Group of Eight industrialised nations told Iran on Thursday to give a "clear and substantive response" next week to an offer by major powers over its nuclear plans, but Tehran said that was unlikely.
Expressing disappointment that Iran had not replied to a June 6 offer of incentives to stop enriching uranium, G8 foreign ministers meeting in Moscow set a deadline of July 5 for Tehran to respond, but did not say where a negative reply would lead.
That is when Iran's top nuclear negotiator, Ali Larijani, is scheduled to meet European Union foreign policy chief Javier Solana somewhere in Europe, possibly Brussels. But in Tehran, two Iranian officials said it was unlikely to happen. Iran has previously said it will answer by August 22.
"We need more time to discuss the offer," an Iranian diplomat told Reuters. The United States has accused Iran of having a secret programme to build nuclear weapons. Iran says it wants only to enrich uranium to a level suitable for use in generating electricity.
In an effort to break a diplomatic deadlock, the five permanent United Nations Security Council members - the United States, Britain, France, China and Russia - and Germany offered Tehran incentives if it stops enriching uranium. The G8 ministers did not say what consequences would arise if Iran failed to deliver a reply next Wednesday or if it rejected the package.
A senior State Department official travelling with US Secretary of State Condoleezza Rice told reporters the six major powers would review progress on July 12, just before a summit of G8 leaders in St Petersburg, Russia, on July 15.
This would allow the six "to make a basic decision about which way this is going," the official said, adding the July 12 meeting was a "signal to the Iranians that they have to make a choice".
Despite the show of unity by the G8 in Moscow - partly backed by a Chinese statement calling for an Iranian response soon - a "no" from Tehran would be likely to divide the powers. Both China and Russia have said they oppose sanctions.
The joint statement issued by the G8 foreign ministers said: "We are disappointed by the absence of an official Iranian response to this positive proposal.
"We expect to hear a clear and substantive response to these proposals at the planned meeting ... on July 5 and to bring these discussions to a rapid conclusion," it added. China's Foreign Ministry spokesman, Jiang Yu, also urged Iran on Thursday to respond "as soon as possible" to the offer.
The G8 statement followed talks between Rice and foreign ministers from Russia, Canada, France, Germany, Italy, Japan and Britain who were in Moscow before next month's G8 summit.
Talks on the incentives package are conditional on Iran freezing uranium enrichment and answering questions about its programme. Iran, the world's fourth largest oil exporter, has refused to suspend its enrichment work.
The Moscow talks focused on Iran, but the G8 also expressed concern about the arrest of 64 Hamas officials by Israeli forces who were preparing to widen an offensive in the Gaza Strip aimed at freeing an abducted soldier.