"We are serious about continuing negotiations and will start next Tuesday with talks," said Ali Larijani, Iran's nuclear negotiator, after meeting Javier Solana, the European Union policy chief.
International leaders have said they want a reply from Tehran by a Group of Eight (G8) summit in St Petersburg on July 15. Tehran has said it will not give a final answer before August 22.
Iran postponed talks with Solana in Brussels on Wednesday, apparently over a visit by an exiled opposition leader to the European parliament, but Larijani said he had agreed to meet Solana for a private dinner on Thursday "out of respect".
Larijani added that formal talks would be held with Solana on Tuesday.
Solana said the process was beneficial to both sides.
Mohamed ElBaradei, head of the International Atomic Energy Agency (IAEA), earlier warned Iran that the world was running out of patience because it had not replied to the proposals.
"The Iranian counterpart authorities told me that they need some time to provide the response," ElBaradei said. "I think they need to make sure that everybody in Iran is on board.
"But by saying that I hope that Iran also understands that the international community is getting somewhat impatient. The earlier they can provide an answer is better for everybody."
The United States has accused Iran of having a secret nuclear weapons programme. Iran, the world's fourth largest oil exporter, denies the charge and says its nuclear programme is solely for power generation.
Iran says its nuclear programme
is solely for generating power
Sean McCormack, US State Department spokesman, kept up the pressure on Iran, telling reporters in Washington: "They've had plenty of time to consider the offer. It's high time that they provide an answer. And we would hope that today is the day that they provide a positive answer."
McCormack said foreign ministers from the United States, Russia, China, Britain, France, Germany and the European Union would meet on Wednesday to discuss whether to impose sanctions on Iran if it has not given a clear answer.
Diplomats admit that Russia and China are unlikely to back any sanctions against Iran at this stage.
Vladimir Putin, the Russian president, urged Tehran to speed up its reply but said talk of sanctions was premature.
"To wait endlessly is counter-productive, but it would be more counter-productive to drive this problem into a dead-end and that is why I would not speak about sanctions at the moment," he said.
The five permanent UN security council members - the US, Britain, France, Russia and China - along with Germany have offered Iran a nuclear reactor with a guaranteed fuel supply as well as economic and security benefits if it halts uranium enrichment.