'Excuse for aggression'

"Iran has accomplished the last stage of the nuclear fuel cycle and [had]  tested two 'new kinds' of enrichment centrifuges with higher capacity."

Mehran Kamrava, the director of the Centre for International and Regional Studies at Georgetown University in Doha, told Al Jazeera: " Ahmadinejad is basically positioning himself ahead of presidential elections in June - he is effectively campaigning.

"Also, he is positioning Iran ahead of dialogue with the US."

Gholam Reza Aghazadeh, Iran's atomic chief, declared Iran had tested "two new kinds" of nuclear centrifuges installed around 7,000 at the Natanz uranium enrichment facility.

The new facility will produce uranium fuel for a planned heavy-water nuclear reactor but western powers fear the reactor could eventually be used for producing a nuclear weapon.

The plant will produce pellets of uranium oxide to fuel the heavy-water research reactor, which is scheduled to be completed in 2009 or 2010.

The US and its allies have expressed concerns Iran could reprocess spent fuel from the heavy-water reactor into plutonium for building a nuclear warhead.