Incentives aimed at persuading Iran to halt sensitive atomic research contain "positive steps" and "ambiguities", its chief nuclear negotiator has said.
Iran has said it will not suspend uranium enrichment
Ali Larijani spoke after receiving the proposal, agreed by world powers last week, from the EU foreign policy chief.
The proposals have not been made public but the BBC News website has learned that they include light water reactors and permission to buy US plane parts.
Tehran says it will consider incentives but refuses to halt enrichment.
Mr Larijani's remarks following his two-hour meeting with Javier Solana were surprisingly upbeat, and here has been a notable absence of angry anti-Western rhetoric, the BBC's Frances Harrison in Tehran reports.
Iran allowed to buy spare parts for civilian aircraft made by US manufacturers
Restrictions lifted on the use of US technology in agriculture
Provision of light water nuclear reactors and enriched fuel
Support for Iranian membership of World Trade Organisation
From Western diplomatic sources
The Iranian negotiator said they had held "constructive" talks and Tehran would respond after studying the incentives.
Europe was right to try to use diplomatic negotiations to solve the problem and Iran was open to resuming talks to try to find a logical and well-balanced solution, he added.
Mr Larijani said the proposals contained some ambiguities that needed resolving without specifying what they were.
However, he talked of the need to resume negotiations to find a logical solution.
The US says it has been heartened by Iran's initial response.
For his part, Mr Solana said he hoped Tehran's reply would be positive.
"Now that the proposal is on the table, I hope we will receive a positive response which will be satisfactory to both sides," he said after talks with Foreign Minister Manouchehr Mottaki.
Mr Mottaki said Tehran would examine the proposals carefully and he was hopeful a final agreement could be reached.
28 April: UN nuclear watchdog say Tehran has ignored calls to halt uranium enrichment
Early May: UN debates draft resolution calling for halt to uranium enrichment
Mid-May: EU countries work on proposals to try to induce Iran to curb atomic programme
31 May: US offers to join direct talks with Iran, in major policy shift
1 June: US, Russia, China and three EU states agree on package of incentives and penalties
6 June: EU foreign policy chief presents proposals in Tehran
Our correspondent says the signs are much more hopeful than last year, when the Europeans offered a package of incentives that Tehran swiftly rejected as too little and too vague.
But she adds that Iran has turned the nuclear issue into one of national pride, and that does it make it difficult to back down without being seen to compromise the country's fierce sense of independence.
Iranian President Mahmoud Ahmadinejad has said Tehran will not abandon its right to nuclear technology under Western pressure and demands that Iran must give up uranium enrichment are unacceptable.
The six powers who drew up the package say Iran should suspend its uranium enrichment programme before any negotiations can begin.
The proposals were agreed by the UK, China, France, Germany, Russia and the US in Vienna.
German Chancellor Angela Merkel said the proposals gave new hope for a diplomatic solution.
Western diplomatic sources have confirmed to the BBC News website that they include permission for Iran to buy spare parts for civilian aircraft made by US manufacturers, and the provision of light water nuclear reactors and enriched fuel.
Other incentives are said to include the lifting of restrictions on the use of US technology in agriculture and support for Iranian membership of the World Trade Organisation.
Western nations fear Iran is enriching uranium to make nuclear weapons, while Tehran says its nuclear programme is for peaceful energy purposes.
The US earlier warned Iran a rejection of the proposals could bring UN-imposed penalties.