A senior official in Teheran said Wednesday that in the next few days, a "surprise" was expected regarding Iran's nuclear program, Al-Jazeera reported.
Teheran's apparent refusal to suspend uranium enrichment set the stage for a showdown at the UN Security Council later this month.
The United States said Wednesday that a proposal by Iran for nuclear negotiations falls short of UN demands for a halt to enrichment, and began plotting "next moves" with other governments.
Diplomats from Europe, the US, Russia and China pored over details of Iran's counterproposal
Wednesday, a day after Teheran presented it.
Initial comments from Russia and China, however, made clear that the US is likely to face difficulty getting at least those nations to agree to any tough sanctions against Iran.
In Paris, French Foreign Minister Philippe Douste-Blazy made clear that his government was sticking by the UN demand for Iran to halt enrichment by the end of this month as a precondition to further talks.
"I want to point out again that France is available to negotiate, and to recall that, as we have always said ... a return to the negotiating table is linked to the suspension of uranium enrichment," Douste-Blazy said.
However, Russia's Foreign Ministry said it would continue to seek a political, negotiated solution to the dispute with Iran over the nuclear program. China appealed for dialogue, urging "constructive measures" by Iran but also urging other parties to "remain calm and patient, show flexibility, stick to the orientation of peaceful resolution and create favorable conditions for resuming talks as soon as possible."
In London, a British Foreign Office spokesman predicted "some hard discussions" when the UN Security Council takes up the Iran issue in the coming weeks. He spoke Wednesday on condition of anonymity under British government regulations.
The White House has so far held off commenting until it can study the offer. But US ambassador to the United Nations, John Bolton, said Tuesday that Washington was prepared to move forward with sanctions against Tehran if the offer was not positive.
The European Union's foreign policy chief, Javier Solana, said the document was "extensive" and required "a detailed and careful analysis" France's foreign minister said Wednesday that the document was complex and that it was consulting with partners on it.
Iran said Tuesday it was ready for "serious negotiations" on its nuclear program and cast the counterproposal as a new formula to resolve the crisis with the West. But a semiofficial news agency said the government was unwilling to abandon uranium enrichment - the key US demand.