Iran's supreme leader said Monday his country was not seeking nuclear weapons, but he vowed that Tehran won't give up its program to enrich uranium for fuel in nuclear reactors.

"If Europeans and others are really worried that we may acquire nuclear weapons, we assure them that we are not seeking to produce such weapons," Ayatollah Ali Khamenei (search) said in his first remarks since Friday's rebuke of Iran's nuclear activities by a U.N. atomic watchdog agency.

"But if they are unhappy about Iran's access to the outstanding nuclear technology and want to stop this trend, I tell them they should be assured that the Iranian nation won't give in on this," he told a gathering of university officials.

Khamenei, who has the final say on all state matters, also said Iran's intention to control the whole nuclear fuel cycle was "essential" to avoiding foreign dependence on nuclear fuel.

Iran repeatedly has said it wants to control the whole nuclear fuel cycle — from extracting uranium ore to enriching it to a low grade for use as fuel in nuclear reactor. Uranium enriched to low levels can be used in power plants, while highly enriched uranium can be used in bombs.

The United States accuses Iran of trying to develop nuclear weapons, while Iran insists its program is aimed only at producing energy. The International Atomic Energy Agency (search) rebuked Iran in a European-drafted resolution for not cooperating enough in the investigation into its nuclear program.

Iran said Saturday it will resume some nuclear activities it suspended under world pressure. Iranian officials have hinted that one area to resume soon is the building of parts for centrifuges used in the uranium enrichment process.

An Iranian opposition group claimed in April that Tehran is aiming to develop a nuclear bomb in the next two years, using secret military facilities in parallel to the civilian program open to international scrutiny. The exiled National Council of Resistance of Iran (search) claimed up to 400 nuclear experts and researchers were working on such secret military programs that answered directly to Khamenei.

Khamenei, however, said Iran's scientists were doing a "huge, essential obligation to prevent (Iran) from dependence on foreigners" for nuclear fuel for power plants.

"It's to preserve national independence," he said.

"And if one day they don't wont to give us fuel for political, international or bilateral reasons, then we won't have running plants," he said.

On Saturday, Iran rejected IAEA demands to stop building a heavy water nuclear reactor in Arak and halt operations of a nuclear conversion facility in Isfahan, both in central Iran.

The Arak plant will produce plutonium that could be used to make nuclear bombs and the Isfahan facility processes uranium powder called yellow cake into hexaflouride gas.

Actual enrichment is injecting hexaflouride gas into centrifuges that spin at high speed, enriching uranium to be used as fuel in reactors.

Last year, under IAEA pressure, Iran suspended enrichment and some other activities and opened facilities to inspections. In response, France Britain and Germany promised to make it easier for Iran to obtain advanced nuclear technology.

According to Hasan Rowhani, Iran's top nuclear negotiator, the three key European powers promised to work toward closing Iran's nuclear dossier by June if Iran stopped making centrifuges.

Iran stopped building centrifuges in April and accused Europeans of reneging on their promise. It says it is no longer committed to its promise.