Iran's president unveiled a new generation of centrifuges used to enrich uranium Friday, defying international warnings against continuing its sensitive nuclear work.
Mr. Ahmadinejad displayed one of the new, domestically-built machines Friday, saying international efforts to pressure Iran on its nuclear program will be met with even more resistance.
The announcement marked Iran's National Nuclear Day.
Also Friday, U.S. President Barack Obama said there is no guarantee that new U.N. sanctions will persuade Iran to change course. However, he added, with "consistent and steady" international pressure, Iran may eventually realize pursuing nuclear weapons is not worth the cost.
During an interview with ABC news, Mr. Obama said Iran is "not a stupid regime" and is intently watching what is happening in the international community.
Thursday, six world powers began negotiations on a possible new round of U.N. Security Council sanctions against Tehran for its nuclear activities.