President Mahmoud Ahmadinejad said Iran has boosted its capacity to enrich uranium, another sign of anti-Western defiance by the leader seeking re-election in a vote next month.

Ahmadinejad said last month that Iran had 7,000 centrifuges at its uranium enrichment facility in Natanz in central Iran. The figure marked a significant boost from the 6,000 centrifuges announced in February. In his latest comments, reported by the state-run Islamic Republic News Agency on Thursday, he did not give a specific new figure.

"Now we have more than 7,000 centrifuges and the West dare not threaten us," IRNA quoted Ahmadinejad as saying on a small radio station late Wednesday.

Ahmadinejad has made Iran's expanding nuclear program one of the centerpieces of his campaign for the June 12 elections and has struck an increasingly harsh tone against the United States and other countries calling for Iran to halt it uranium enrichment.

Iran's leaders say they will never give up nuclear technology and insist they seek only energy-producing reactors. The United States, Israel and other nations worry that Iran's enrichment facilities could eventually produce material for nuclear warheads.

There is broad consensus among Iranian voters on the nation's rights for a nuclear program. But Ahmadinejad's three challengers — a fellow hard-liner and two moderates — have questioned his uncompromising stances against the West and their offers of economic incentives in exchange for suspending uranium enrichment.

The centrifuges spin at supersonic speeds to remove impurities from uranium gas, which then goes through other steps to become nuclear fuel or, at higher enrichment levels, nuclear weapons material.

Earlier this year, Iran said it was using an upgraded centrifuge that produces enriched uranium at about double the rate of its original systems.

Currently, Iran is only capable of slowly producing enriched uranium for reactors. But Iranian officials have said their long-term goal is for more than 50,000 centrifuges, which would give it the ability to produce high-grade nuclear material in a start-to-finish cycle of just weeks.