Tehran: President Mahmoud Ahmadinejad said on Saturday that Iran has boosted the number of uranium-enriching centrifuges to up to 6,000, in an expansion of its nuclear drive that defies international calls for a freeze.

"Today they [the West] have consented that the existing 5,000 or 6,000 centrifuges not be increased and that operation of this number of centrifuges is not a problem," Ahmadinejad was quoted as saying by state radio.

Ahmadinejad said in April that Iran was working to install 6,000 more centrifuges at an underground hall in a plant at its nuclear facility in Natanz, where it already had 3,000 running. It is a major expansion of Iran's nuclear programme, which the West fears could be aimed at making atomic weapons.

"Iran does not negotiate with anyone over its obvious nuclear right," Ahmadinejad said in the city of Mashhad. State radio quoted him as saying the West had retreated in the dispute and had now "accepted that Iran would continue uranium enrichment with its current 6,000 centrifuges".

Iran says it aims eventually to have 50,000 centrifuges to produce fuel for a planned network of power plants. Enriched uranium can also provide material for arms if refined further. If running smoothly for long periods, 3,000 would be enough to make material for a warhead in a year, Western experts say.