"Since Iran has mastered nuclear technology, the sanctions will have no effect," said Iran's chief nuclear negotiator Ali Larijani, according to the official IRNA news agency.

"Nuclear technology is a strategic technology of (Iran's) Islamic system and Iran will not take a step back," he added.

His comments came after British Prime Minister Gordon Brown warned this week that London would support a third United Nations resolution imposing sanctions against Iran if Tehran does not scale back its nuclear programme.

France, a fellow veto-wielding permanent member of the UN Security Council, has also said it is considering "additional sanctions" against Tehran.

Iran last month agreed with the UN watchdog International Atomic Energy Agency (IAEA) on a timetable to answer outstanding questions over its nuclear programme, and diplomats have said this is likely to stave off the threat of sanctions for a few more months.

But the United States, which accuses Iran of seeking an atomic weapon, has expressed great suspicion over the accord, saying the agreement does not go far enough.

The Security Council has already passed two resolutions imposing sanctions against Iran and calling on the Islamic republic to halt sensitive uranium enrichment work, something it has so far refused to do.

President Mahmoud Ahmadinejad said last week Iran had reached a key goal by putting into operation more than 3,000 uranium-enriching centrifuges, although this figure was higher than recently reported by the IAEA.

Iran insists the atomic drive is solely aimed at generating electricity and that its growing population will need nuclear power as fossil fuels start to run dry.

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France mulling non-UN sanctions against Iran
France is considering fresh sanctions to pressure Iran to halt its nuclear programme, holding talks with investors on measures that could be adopted outside the UN, the presidency said Thursday.

"Our priority today is the adoption of a third resolution within the framework of the United Nations Security Council," President Nicolas Sarkozy's spokesman David Martinon told a press briefing when asked about the possibility of bilateral sanctions against Iran.

"The project we are working on... is more about additional sanctions," he said.

Asked whether France would ask multinationals such as car manufacturer Renault or oil giant Total to suspend their activities in Iran, Martinon said: "We are in contact with the French investors."

On Tuesday, the French foreign ministry said that new sanctions against Tehran should be taken "as a priority" within the UN framework, but did not rule out using another forum such as the European Union.

Officials however have said that France is unlikely to opt for unilateral sanctions to punish Tehran for its failure to halt sensitive nuclear activities.

Iran warned on Sunday it would "reconsider" its cooperation with the International Atomic Energy Agency (IAEA) if the Security Council imposed a third set of sanctions over its contested nuclear programme.

Tehran agreed a timetable with the UN atomic agency last month to answer outstanding questions over its atomic drive, in a move that is expected to stave off the threat of sanctions for several months.

The United States accuses Tehran of seeking to acquire nuclear weapons -- an allegation vehemently denied by the Islamic republic -- and has never ruled out taking military action against it.