Iran's top nuclear official said on Thursday that United Nations sanctions would not restrict its atomic program, and that it was continuing to amass the raw material for uranium enrichment.
The UN Security Council voted unanimously on December 23 to impose sanctions on Iran's trade in sensitive nuclear materials and technology in an attempt to stop enrichment work that could produce the material for nuclear explosives.
"They [the West] should accept that this [nuclear work] is our national right and is irreversible," Gholamreza Aghazadeh, the head of Iran's Atomic Energy Organization, was quoted as saying by the student news agency ISNA.
"This technology is Iranian-made and cannot be limited by sanctions."
Analysts say that to achieve its goal of "industrial-scale" enrichment with 54,000 centrifuge enrichment machines -- only around 350 are known to be operating experimentally so far -- Iran may still need to acquire equipment abroad.
Aghazadeh said Iran had now stockpiled 250 tonnes of uranium hexafluoride gas (UF6), the feedstock that is injected into centrifuges for enrichment into fuel.
"Today we have produced more than 250 tonnes of UF6, kept in tunnels that are almost unique in the world," he said.
The latest figures from the International Atomic Energy Agency [IAEA] say Iran had stockpiled a total of 165 tonnes of UF6 as of early November 2006.
Mark Fitzpatrick, nuclear non-proliferation analyst at London's International Institute for Strategic Studies, said 250 tons of UF6, if enriched to 90 percent or higher, would yield enough fuel for up to 50 nuclear warheads.
Iran has so far enriched token amounts of UF6 only to the 3-5 percent level required for power plant fuel. It says it has no intention of refining UF6 to the high level needed for bombs.
Aghazadeh repeated Iran's call for talks to resolve the dispute with the West, which believes Tehran wants to build nuclear warheads despite Iran's insistence that it wants to make fuel to generate electricity.
"We are ready to build confidence," he said.
In reaction to the UN resolution, Iran's parliament passed a bill last week obliging the government to revise its level of cooperation with the IAEA and to accelerate its nuclear work.
The bill gave President Mahmoud Ahmadinejad's government a free hand to decide whether it wanted to quit the nuclear Non-Proliferation Treaty (NPT) if pressured.
But Aghazadeh said Iran, the world's fourth largest oil exporter, had no intention of pulling out of the NPT.