The United States is leading efforts to isolate Iran over what Washington says is Tehran's covert bid to build nuclear weapons. Iran denies the charge, saying its plans are peaceful.
Diplomats last week told Reuters an inquiry by the U.N. International Atomic Energy Agency into whether Iran covertly researched how to assemble an atom bomb appeared to have stalled while Tehran expanded its sensitive uranium-enrichment work.
The diplomats said they expected this to be reflected in the IAEA report due out later on Monday but said they did not have details about what the report in its final form would contain.
"So what we are expecting (from) the agency … (is) to conduct itself based on its own regulations and not to be affected by outside pressure, including U.S. pressure," Foreign Ministry spokesman Hassan Qashqavi told a news conference.
"We are fully expecting the IAEA to remain independent again, to confine its activities to recognized international laws and regulations," Qashqavi said in comments broadcast and translated by the state-run English satellite channel Press TV.
The IAEA said in May Iran seemed to be withholding information needed to explain intelligence allegations that it had fused projects to process uranium, test high explosives and modify a missile cone in a way suitable for a nuclear warhead.
Tehran has dismissed the mainly U.S. intelligence on "weaponization" research as fabricated or irrelevant. Iran says it has been cooperating with the agency within IAEA rules.
Qashqavi said that "working with the agency has to fall within the parameters of the regulations and also the safeguards and our agreements with the agency".
"We are always ready for the continuation of our cooperation within the confines of the modality for agreement," he said but added Iran would need time "to study, to analyze" the report before commenting on its contents.
Diplomats say the IAEA is likely to show Iran has gradually expanded its enrichment capacity, work which can be used to make power plant fuel or material for bombs if refined much more.
Iran, the world's fourth biggest oil producer which sits on the second largest gas reserves, says it needs nuclear power plants so it can save more of its hydrocarbons for export.
But it has failed to convince world powers of its peaceful intentions, prompting the U.N. Security Council to impose three sets of limited sanctions.
The United States wants a fourth set, but analysts say Washington's row with Russia over Georgia could hinder agreement at the United Nations about imposing new penalties.
(Writing by Edmund Blair)
