Iran has said it will respond by mid-August to a package of incentives on its nuclear programme offered by UN Security Council nations plus Germany.
Tehran insists its nuclear programme is for energy purposes
Iranian President Mahmoud Ahmadinejad made the announcement on state TV.
After an EU-US summit in Vienna, US President George W Bush said it was a "long time" to answer a "reasonable deal" that was offered on 6 June.
The US believes Iran is trying to make nuclear weapons but Tehran insists the programme is for energy purposes.
President Ahmadinejad told a crowd in western Iran in a broadcast speech: "We are studying the proposals. Hopefully, we will present our views about the package by mid-August."
The package is said to offer help with Iran's civilian nuclear programme and to guarantee supplies of reactor fuel, as well as various trade advantages and security guarantees.
It requires Iran to halt its production of enriched uranium, which can also be used in nuclear warheads.
President Ahmadinejad said Iran was still studying the package
But in his speech, President Ahmadinejad again stressed Iran had "definite and legitimate rights" to a nuclear programme.
"We will negotiate with everyone... but negotiations should be as equals and without any preconditions imposed," he said.
Iranian Foreign Minister Manouchehr Mottaki is to meet his German counterpart, Frank-Walter Steinmeier, in Berlin on Saturday to discuss the situation.
The issue was also high on the agenda at the EU-US summit which took place in Vienna on Wednesday.
Chancellor Wolfgang Schuessel of Austria, which holds the European Union's rotating presidency, said Iran had "to make the right choice" and curtail its nuclear ambitions.
President Bush said world powers were united to prevent Iran from acquiring the know-how to make nuclear weapons.
He said: "It should not take the Iranians that long to analyse what is a reasonable deal."
The US has warned it will step up pressure and push for sanctions if Iran rejects the package.
Analysts say there may be divisions in the Iranian hierarchy, with some favouring outright rejection and some acceptance as long as certain requirements are changed.