Iran said that inspectors from the UN nuclear watchdog agency would remove seals from some nuclear facilities by yesterday, opening the way for Tehran to resume research on fuel production.
The development heightened concerns that Iran was moving toward building atomic weapons.
"Iran is ready to resume the research activities after the inspectors remove the seals," Foreign Ministry spokesman Hamid Reza Asefi said.
"It is our right as [much as] other members of the Nonproliferation Treaty. Iran should not be exempted,'' he said.
Inspectors from the International Atomic Energy Agency (IAEA) arrived in Tehran on Saturday to remove seals they had affixed to the research sites after Iran voluntarily agreed to stop all enrichment-related activities more than two years ago as a confidence-building measure.
The Iranians have maintained they will never give up their right under the Nonproliferation Treaty to enrich uranium and produce nuclear fuel, but the IAEA and most of its members want Tehran to maintain the freeze because of growing fears it will misuse enrichment to make weapons.
Iran told the IAEA last week it would resume research yesterday, and officials said talks with the inspectors over restarting the research could wrap up by yesterday at the latest, the official Islamic Republic News Agency said. Iran has not specified the type of research.
Tehran says its nuclear program is for electricity generation, while the US and Europe suspect Iran is moving to produce nuclear bombs. The US and France have pushed for taking Iran before the UN Security Council, which could impose sanctions if Tehran is found in violation of the Nonproliferation Treaty.
Asefi said Iran's research would respect regulations set by the UN watchdog and the treaty.
In Vienna, Austria, the tug of war continued on Sunday between Iran and the IAEA, which asked for additional details about what Tehran planned to do with its enrichment equipment.
IAEA spokeswoman Melissa Fleming said the agency had received additional information since Saturday, when Tehran first provided the agency with some specifics, but it still sought more.
Last Thursday a high-ranking Iranian delegation failed to show up for a scheduled meeting with IAEA head Mohamed ElBaradei, thereby reneging on a pledge to provide full details of its plans.