Vice President Gholam Reza Aghazadeh said Iran will continue to install more centrifuges and enrich uranium to produce nuclear fuel for future Iranian nuclear power plants. In August, Iran said it had 4,000 centrifuges running at its plant in the central city of Natanz.
Uranium enriched to a low level is used to produce nuclear fuel, but further enrichment makes it suitable for use in nuclear weapons.
"At this point, more than 5,000 centrifuges are operating in Natanz and enriching uranium," said Aghazadeh, who is head of the Atomic Energy Organization of Iran. He spoke to reporters during an exhibition of Iranian nuclear achievements at Tehran University.
Flaunting Iran's defiance of international demands, Aghazadeh said the Islamic Republic will never suspend enrichment.
"Suspension has not been defined in our lexicon," he said.
The U.N. nuclear watchdog, the International Atomic Energy Agency, said in a report last month that Iran was installing, or preparing to install, thousands more of the machines that spin uranium gas to enrich it - with the target of 9,000 centrifuges by next year.
IAEA officials could not be immediately reached for a comment Wednesday, but Iran has previously said it plans to move toward large-scale uranium enrichment that will ultimately involve 54,000 centrifuges.
Former U.N. nuclear inspector David Albright said the additional centrifuges announced Wednesday were expected.
"Expect another 1,000 to start enriching soon," said Albright, president for the Washington-based Institute for Science and International Security. "As Iran runs centrifuges more and more, it's just going to get better at it."
Earlier this month, the IAEA estimated Iran had around about 1,400 pounds of low-enriched uranium. U.N. officials have said Tehran would have to produce a little more than twice that to begin enriching it to the level needed to produce a nuclear weapon.
The United States and some of its allies accuse Iran of seeking to build nuclear weapons, and the U.N. Security Council has imposed three rounds of sanctions on Iran for its refusal to freeze its uranium enrichment program.
But Tehran denies it is trying to build bombs and insists it has the right under the Nuclear Nonproliferation Treaty to enrich uranium and produce reactor fuel.
In Washington, Secretary of State Condoleezza Rice said had not seen the report on the new centrifuges but stressed that Iran was continuing to pursue enrichment and reprocessing capability.
"They are continuing to try to perfect the technologies that could lead to a nuclear weapons technology. And that is what the international coalition that we have put together ... is trying to stop," she told reporters.
At the exhibition in Tehran, Iran for the first time put on public display one of its P-1 centrifuges, and officials at the exhibition explained the machine to visitors. During the enrichment process, uranium gas is spun in a series of centrifuges known as "cascades" to purify it.
Aghazadeh also said Iran had made "good progress" in constructing a 40-megawatt heavy-water reactor near Arak in central Iran.
"The heavy water plant is experiencing a production beyond its capacity," he said without elaborating.
Western countries have repeatedly called on Iran to stop construction of the reactor, fearing it could be used as a second track toward building a warhead.
When it is finished, the Arak reactor could produce enough plutonium for a nuclear weapon each year, experts have said.
Aghazadeh also claimed Iran has conducted research on nuclear fusion, but he didn't provide more details on the research other than to say it started "long ago."
Nuclear fusion, the process behind the hydrogen bomb, is more powerful than fission and scientists have long tried to harness it as an energy source.
Also Wednesday, Iranian state television reported that the country successfully launched a second rocket into space, following up on the first such launch in February.
The rocket, entitled "Kavoshgar 2," or Explorer 2, made it to the lower reaches of space and returned to earth 40 minutes later on a parachute. It wasn't clear when the launch took place, and no other details were available.
Iran has long held the goal of developing a space program, generating unease among world leaders already concerned about its nuclear and ballistic missile programs.