President Mahmoud Ahmadinejad said Sunday his country would move forward with its disputed nuclear program, comparing its nuclear drive to a train that has no brakes.

The hard-line leader also repeated his call for negotiations, saying the time for "bullying" had expired. International leaders have demanded that Iran halt uranium enrichment.

"The train of the Iranian nation is without brakes and a rear gear," the radio quoted Ahmadinejad as telling a gathering of Islamic clerics. "We dismantled the rear gear and brakes of the train and threw them away sometime ago."

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The International Atomic Energy Agency last week reported that Iran had ignored a U.N. Security Council ultimatum to freeze its uranium enrichment program and instead had expanded the program by setting up hundreds of centrifuges.

The report came after a U.N Security Council deadline expired Wednesday for Iran to stop enrichment. Iran has repeatedly refused to halt enrichment as a precondition to negotiations about its program.

The United States and its Western allies have insisted Iran must suspend enrichment before any negotiations over its nuclear program.

Iran, which has rejected that condition, insists its program is peaceful. But the United States and its allies accuse Tehran of using its energy program as a cover to develop weapons.

Ahmadinejad said Sunday that Western countries feel threatened by Iran's nuclear program because they feel their own powers are diminishing.

"The Westerners are not concerned about the existence and activity of ... centrifuges in Iran; they are concerned about the collapse of their hegemony and hollow power," the radio quoted Ahmadinejad as saying.

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