Iran voiced defiance on Saturday in the face of Western condemnation over a new nuclear fuel plant, with a senior official saying the facility would soon be operational and make the 'enemies blind'.

US President Barack Obama demanded on Friday that Iran come clean about its nuclear programme or risk 'sanctions that bite' after the disclosure of the new uranium enrichment plant under construction southwest of Tehran.

On Saturday, Obama said the discovery of the facility showed a 'disturbing pattern' of evasion by Tehran which added urgency to its planned talks with world powers in Geneva on Thursday.

The West accuses Iran of seeking to acquire a nuclear weapon. Tehran insists its nuclear activities are aimed at generating electricity so that it can export more oil and gas.

Iran acknowledged the existence of the uranium enrichment facility near the holy city of Qom for the first time on Monday in a letter to the U.N. International Atomic Energy Agency.

US officials said the disclosure was aimed at pre-empting an announcement by Western governments, which were aware of the site, but Iranian President Mahmoud Ahmadinejad said the facility was legal and open for inspection by the IAEA.

'This new plant, God willing, will soon become operational and will make the enemies blind,' the semi-official Fars News Agency quoted Mohammad Mohammadi-Golpayegani, who heads the office of Supreme Leader Ayatollah Ali Khamenei, as saying.

On Friday, Ahmadinejad said the facility was around 18 months from starting operations and that Western powers would regret accusing Iran of hiding it. Iran already has a uranium enrichment plant near the central city of Natanz.

Mohammadi-Golpayegani, a cleric who was speaking at a ceremony marking the start of the 1980-88 Iran-Iraq war, said the construction of the facility was a sign Iran was at the 'summit of power', Fars reported.

Obama, British Prime Minister Gordon Brown and French President Nicolas Sarkozy, in Pittsburgh for a Group of 20 summit, made a joint appearance on Friday to level the new charges against Iran over its nuclear programme.

Obama said Tehran had been building the nuclear plant in secret for years and urged it to address international concern that its nuclear programme is geared toward making bombs.

'This is a serious challenge to the global nonproliferation regime and continues a disturbing pattern of Iranian evasion,' Obama said in his weekly radio and Internet address on Saturday.

'That is why international negotiations with Iran scheduled for Oct. 1 now take on added urgency,' he said.

Iran will meet the United States and five other powers in the Swiss city of Geneva.

Britain, France and Germany have joined the United States in raising the spectre of new sanctions against Iran if it does not take steps to address concerns about its nuclear work.

Russia also signalled a greater willingness to go along with sanctions while China said it favoured a 'dual track' approach of pressure and talks.

But Iran, which has repeatedly rejected demands to halt its nuclear programme, is showing no sign of backing down.

Alaeddin Boroujerdi, who heads the Iranian parliament's national security and foreign policy commission, warned the West against taking measures which he suggested could affect Tehran's existing co-operation with the IAEA.

'They should not do something that would make Iran regretful of the existing level of cooperation which is sometimes beyond the agency's legal requirements,' he was quoted as saying by ISNA news agency.

Boroujerdi said Iran's construction of a new enrichment plant should not negatively overshadow the October talks, 'unless these countries are after some pretext to ruin the negotiations and to make them fruitless.'-