The head of the United Nations nuclear watchdog has praised Iran's better co-operation with global non-proliferation efforts as a "sea change".
Tehran insists its nuclear programme is for energy
"We are clearly moving in the right direction," Mohammed ElBaradei, who heads the International Atomic Energy Agency (IAEA), told reporters.
Last week, the IAEA expressed concern over Iran's failure to declare aspects of its nuclear programme.
Iran agreed last year to make a full disclosure of its nuclear activities.
The United States has accused Iran seeking nuclear weapons, but the government in Tehran says its nuclear programme is for purely peaceful purposes.
'Light at the end of the tunnel'
"If you compare where we were a year ago and where we are today, that's a sea change," Mr ElBaradei told reporters before meeting European Union foreign policy chief Javier Solana in Brussels.
"I hope, sometime in the future - should Iran continue to co-operate, continue to give us all the details - we should be able to see some light at the end of the tunnel," Mr ElBaradei said.
He said he was confident Iran would comply with its commitment.
However, Mr ElBaradei refused to comment on whether IAEA was likely to censure Tehran when the agency meets next week in Vienna.
In its report last week, the IAEA said Iran had not declared designs for the advanced P-2 centrifuge used to make bomb-grade material.
The report, obtained by the BBC, said Iran had also experimented with polonium, a radioactive substance that can trigger a nuclear blast.
Western diplomats said the report raised questions about Tehran's readiness to co-operate with the UN.
Iran said the traces of enriched uranium and polonium were the result of contamination of components imported for legitimate nuclear power programmes.
The IAEA said it was in contact with Pakistan to verify the claim.
And the agency welcomed Iran's agreement to suspend enrichment activities and to stop the assembly and testing of centrifuges, saying it would help to build confidence.