Iran has said it will tell investigators where their planned plants are
Iran will inform UN nuclear inspectors where 10 planned installations are only six months before they become operational, Tehran has said.
Friday's announcement came after the US warned Iran that "time was running out" if it wanted to avoid sanctions over its nuclear programme.
International inspectors have demanded information on all planned facilties.
It maintains that its programme is peaceful, despite international fears it is trying to build nuclear weapons.
Iran argues that under international agreements it is only required to give 180 days' notice before it begins operating a new facility.
But the UN's nuclear watchdog, the International Atomic Energy Agency, says that Iran must abide by a subsidiary agreement it signed in 2003 and give information on plants still at the design stage.
Tehran has continued to defy the six nations - the US, UK, France, Germany, China and Russia - trying to negotiate a deal over their nuclear material.
President Mahmoud Ahmadinejad announced last week that his country would build another 10 secret facilities to enrich uranium, although experts doubt whether it has the resources to do so.
He has also said Iran plans to enrich uranium to 20%, a higher level than at present.
On Friday Iranian officials said they would allow nuclear inspectors in to the plants six months before they started up centrifuges used to enrich uranium.
Iran has also rejected a deal suggested by negotiators to allay international fears that it is attempting to enrich uranium to the degree necessary to make a nuclear weapon.
The deal would have regulated Iran's access to its nuclear material by sending it abroad to be enriched.
Under the plan, the return of the enriched uranium would be controlled and its use limited to use in a reactor near Tehran which is monitored by the International Atomic Energy Authority.
Last week, the IAEA voted to rebuke Iran for building a second facility in secret under a mountain near the city of Qom.
On Thursday Iran's Parliament responded saying it would review relations with counties that had backed the condemnation of the Tehran government at the IAEA.
Russia, previously considered an ally of Iran, had joined the vote.
But on Thursday Russia's Prime Minister Vladimir Putin apparently eased its pressure on Iran, declining to answer a question on possible sanctions at a televised question-and-answer session.
Russia had "no information that Iran is working on the creation of a nuclear weapon" Mr Putin said.
Civilian nuclear power requires uranium enriched to about 3%, but weapons grade uranium needs to be enriched to 90%.
Iran has declared its intention to enrich uranium to 20%.
Existing UN sanctions are meant to prevent the flow of any items or technology which might aid Iran in enriching uranium or developing nuclear weapon delivery systems.
But further sanctions might be imposed if diplomacy fails, negotiators say.
"Time is running out. That deadline is the end of the year," White House spokesman Robert Gibbs told journalists on Wednesday.