Russia and France would process uranium for Iran under the deal
Iran will accept a UN deal on its nuclear programme, but only if "very important changes" are made, Iranian state media have reported.
Al Alam TV quoted "informed" sources as saying Tehran would respond to the International Atomic Energy Agency (IAEA) deal within 48 hours.
Under the draft proposal, Iran would send its enriched uranium to Russia and France to be turned into fuel.
Iran missed a Friday deadline for responding to the IAEA's proposal.
All the other parties have confirmed their support for the deal, which is seen as a way for Tehran to get the fuel it needs for an existing reactor, while giving guarantees to the West that its enriched uranium will not be used for nuclear weapons.
Al Alam said Iran would "accept the broad framework of the deal, but wants very important changes in it".
The station gave no further details on the changes Iran was reported to have requested be made to the draft.
On Monday, Foreign Minister Manouchehr Mottaki said Iran was considering whether to send some of its uranium stock to other countries for enriching or to buy already enriched uranium.
Mr Mottaki said the decision would be announced within days.
Jon Leyne, BBC News Tehran correspondent
The latest hint from Al Alam TV suggests that Iran will accept a deal to supply fuel for its Tehran research reactor. But those countries dealing with Iran will wonder what "important changes" Tehran wants in response.
In particular, is Iran willing to ship its own enriched uranium out of the country? On Monday the Iranian foreign minister said maybe Iran would agree, maybe it would not.
The other question observers are asking is how much this is a case of genuine indecision by Iran, and to what extent is it just playing for time?
The answer could be that those in power are quite content to let a genuine debate rumble on, knowing that it also buys time, staving off new sanctions, while Iran presses ahead with its nuclear programme.
French Foreign Minister Bernard Kouchner said that all the other parties in the talks had shown "a great deal of patience", and he accused Tehran of wasting time.
The AFP news agency quoted Mr Kouchner as saying that Mr Mottaki "makes declarations and more declarations" which "rarely provoke enthusiasm" and are "rarely very positive".
"We have been waiting for light at the end of the tunnel for almost three years. We will wait until we decide that enough is enough and that the process is exhausted," said Mr Kouchner.
"One day it will be too late."
EU foreign ministers had hoped to have a reply from Iran by Tuesday, in time for high-level meetings in Luxembourg.
The EU's Foreign Policy Chief Javier Solana said the UN had offered "a good deal" and did not require "fundamental changes", Reuters reports.
Opposition inside Iran to the agreement is said to be growing. The BBC's Tehran correspondent, Jon Leyne, says that if it is approves, it would offer some evidence that negotiations with Iran can bear fruit.
But if Tehran rejects it, the wider talks process would face a bleak future and new sanctions would once again be on the agenda, he adds.
NUCLEAR FUEL CYCLE
Mined uranium ore is purified and reconstituted into solid form known as yellowcake
Yellowcake is converted into a gas by heating it to about 64C (147F)
Gas is fed through centrifuges, where its isotopes separate and the process is repeated until uranium is enriched
Low-level enriched uranium is used for nuclear fuel
Highly enriched uranium can be used in nuclear weapons
On Sunday, a team from the UN watchdog, the International Atomic Energy Agency (IAEA) began an inspection of an Iranian uranium plant.
The Fordo plant, built into a mountainside near the city of Qom, was previously secret.
Its existence was announced by the Iranian authorities last month, apparently because Western intelligence agencies had already discovered it, says our correspondent.
Iran agreed to open the site to monitoring at talks with the five permanent members of the UN Security Council plus Germany in Geneva on 1 October.
The inspectors are not expected to report until they leave Iran, but some Iranian officials have already said the inspection shows their country's nuclear activities are both transparent and peaceful.
Iran says its nuclear programme is for purely peaceful purposes, but the revelation of the existence of the new plant increased fears in the West about Tehran's intentions.