"We are against offering the agency an open door once more and that they expect Iran to respond to any claim," said Alaeddin Borujerdi, the head of parliament's national security and foreign affairs commission.

He was commenting on a report issued Monday by the International Atomic Energy Agency which accusing Iran of stalling over a probe into its nuclear work and of continuing uranium enrichment in defiance of UN demands.

"We do not think there should be an open forum so America can bring up a new claim every day and pass it on to the agency, expecting Iran to address any claim," he was quoted as saying by the state news agency IRNA.

Iran's envoy to the UN agency also warned that Tehran would only cooperate within the framework of the nuclear Non-Proliferation Treaty and its safeguard agreements.

"We continue cooperating with the IAEA but they should not expect us to apply the additional protocol," Ali Asghar Soltanieh told state television.

Iran stopped applying the additional protocol, which gives inspectors broader access to its nuclear sites, after the nuclear case was referred to the UN Security Council in 2006.

The IAEA complained it was making little headway in investigating allegations that Tehran has been involved in studies to make a nuclear warhead, as Iran refused to provide access to documentation, individuals or sites which could reveal the true nature of its activities.

Tehran said the alleged weapon-related studies were based on fabricated documents and it provided the IAEA a 117-page response in May addressing some of the agency's questions.

The United States, which is spearheading moves against Iran's nuclear drive, warned that Tehran could face possible new sanctions in the wake of the IAEA report.

Uranium enrichment lies at the core of fears about Iran's nuclear programme, as the process can make nuclear fuel as well as the fissile core of an atom bomb.

Iran denies Western claims it is seeking to build atomic weapons, insisting that it wants nuclear power to provide energy for a growing population.

It is currently running close to 4,000 uranium enrichment centrifuges in a plant in Natanz in central Iran and installing several thousand more as well as testing more advanced centrifuges.

According to a study by the US-based Institute for Science and International Security, Iran is making significant progress on developing and operating its centrifuges.

"The centrifuges now appear to be running at approximately 85 percent of their stated target capacity, a significant increase over previous rates," the ISIS said in a report carried on its website Monday.

It said the centrifuges had been running at 50 percent capacity, mainly owing to breakage and instability, following the release of IAEA's previous report on Iran in May.

"This latest report, however, shows that Iran has largely overcome these problems," the ISIS said.

The IAEA said Iran has produced a total of 480 kilogrammes (1,058 pounds) of low-enriched uranium since the resumption of enrichment in February 2007.

An IAEA official, speaking on condition of anonymity on Monday, said Iran would need 1,700 kilogrammes (3,752 pounds) of low-enriched uranium to make an atom bomb.

But the ISIS said: "Under optimal conditions, Iran could use between 700 and 800 kilogrammes of LEU to produce in its P1 centrifuges 20-25 kilogrammes of weapons-grade uranium, enough for a crude fission weapon."

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