Iran Celebrates National Nuclear Day.

TEHRAN (FNA)- Iran on Tuesday marks its new national day celebrating the achievements of its nuclear program with speeches by top officials including President Mahmoud Ahmadinejad.

For the second year the Islamic Republic is staging its "national day of nuclear achievement" commemorating the April 2006 anniversary of Iran's first production of uranium sufficiently enriched to make atomic fuel.

On Tuesday morning president Ahmadinejad spoke at Iran's most important nuclear facility of Natanz, where engineers have built around 3,000 P1 centrifuges at an underground facility to enrich uranium.

Iran has in recent months also started experimenting with more efficient P2 centrifuges at an above-ground test facility at the plant - the latest example that it has no intention of giving in to Western pressure to halt enrichment.

Ahmadinejad will later attend a major ceremony at 1600 GMT at the headquarters of Iran state broadcasting in Tehran alongside the head of Iran's atomic energy organization Gholam Reza Aghazadeh.

Some reports have claimed that Iran has expanded the number of centrifuges at Natanz with more advanced models but this has not been confirmed by Iranian officials.

But they have also hinted that the country is preparing to announce "good news" about progress in the nuclear program on Tuesday.

Iran insists that its nuclear program is entirely peaceful and solely aimed at generating energy for a growing population whose supply of fossil fuels will eventually run out.

Tehran has repeatedly insisted that it has no intention of making concessions over the key issue of uranium enrichment.

"The government rejects any package of incentives that calls for the suspension of enrichment or undermines the Iranian nation's nuclear rights," said Foreign Ministry Spokesman Seyed Mohammad Ali Hosseini here on Monday.

The US is at loggerheads with Iran over Tehran's independent and home-grown nuclear technology. Washington has laid much pressure on Iran to make it give up the most sensitive and advanced part of the technology, which is uranium enrichment, a process used for producing nuclear fuel for power plants.

Washington's push for additional UN penalties contradicted the recent report by 16 US intelligence bodies that endorsed the civilian nature of Iran's programs. Following the US National Intelligence Estimate (NIE) and similar reports by the IAEA head - one in November and the other one in February - which praised Iran's truthfulness about key aspects of its past nuclear activities and announced settlement of outstanding issues with Tehran, any effort to impose further sanctions on Iran seemed to be completely irrational.

The February report by the UN nuclear watchdog, the International Atomic Energy Agency, praised Iran's cooperation in clearing up all of the past questions over its nuclear program, vindicating Iran's nuclear program and leaving no justification for any new UN sanctions.

Tehran says it never worked on atomic weapons and wants to enrich uranium merely for civilian purposes, including generation of electricity, a claim substantiated by the NIE and IAEA reports.

Iran has insisted it would continue enriching uranium because it needs to provide fuel to a 300-megawatt light-water reactor it is building in the southwestern town of Darkhoveyn as well as its first nuclear power plant in the southern port city of Bushehr.

Not only many Iranian officials, including President Mahmoud Ahmadinejad, but also many other world nations have called the UN Security Council pressure unjustified, especially in the wake of recent IAEA reports saying Iran had increased cooperation with the agency.

US President George W. Bush, who finished a tour of the Middle East in winter has called on his Arab allies to unite against Iran.

But hosting officials of the regional nations dismissed Bush's allegations, describing Tehran as a good friend of their countries.

Bush's attempt to rally international pressure against Iran has lost steam due to the growing international vigilance, specially following the latest IAEA and US intelligence reports.