The UN nuclear watchdog is preparing to issue a report on investigations into Iran's nuclear activities.
The report will include an agreement Iran reached with EU states last week to halt uranium enrichment plans.
Iran is facing a 25 November deadline to comply with an International Atomic Energy Agency (IAEA) resolution ordering the suspension.
The agreement to halt enrichment is expected to ward off the threat of UN sanctions, correspondents say.
The IAEA report will cover two decades of what the US views as clandestine nuclear activities aimed at developing the capacity to build nuclear weapons.
Sanction threat easing
IAEA board members from 35 countries will review the report on 25 November before deciding if Iran is in breach of a resolution, passed in September, calling for the suspension of uranium enrichment and related activities.
The US has pushed for the IAEA to refer Iran to the UN Security Council, which has the power to impose sanctions.
The BBC's Bethany Bell in Vienna, where the IAEA is based, says if the European enrichment freeze can be verified over the next few days, the US is unlikely to have enough support to send Iran to the Security Council.
The EU has offered to Iran increased co-operation on trade and energy in exchange for the freeze.
Successful uranium enrichment could be seen as a key stage in the development of weapons-grade nuclear material.
On Sunday chief Iranian negotiator Hassan Rohani said the suspension would be in force until a final settlement is reached.
Speaking in Tehran, Mr Rohani said Iran would suspend "almost all" its enrichment activities until a long-term agreement on Iran's nuclear programme is reached.
Talks will begin next month, he added.
Another senior negotiator, Hossain Mousavian, told Iranian state television the agreement was a "confidence-building" move and not a legal obligation.
He stressed that the suspension was temporary, the Associated Press news agency reported.
A deal reached last year between the EU and Iran on a uranium-enrichment freeze later unravelled.
Iran has said it has a legal right to nuclear energy - and in particular to securing their own source of fuel for power stations, rather than being dependent on outsiders.