Defiant move will further aggravate tensions between Iran and major powers over its nuclear activities.
Iran announced plans on Sunday to build 10 new uranium enrichment plants in a major expansion of its atomic programme, just two days after the UN nuclear watchdog rebuked it for carrying out such work in secret.
The defiant move by hardline President Mahmoud Ahmadinejad's government will further aggravate tensions between the Islamic Republic and major powers over Iranian nuclear activities.
Analysts said it would accelerate calls for more UN sanctions against Iran. One said it increased the chances of military action to halt an atomic programme that Washington and its allies suspect is aimed at building a nuclear bomb, something Tehran strongly denies.
The White House condemned the announcement.
"If true, this would be yet another serious violation of Iran's clear obligations under multiple UN Security Council resolutions and another example of Iran choosing to isolate itself," spokesman Robert Gibbs said in a statement.
"Time is running out for Iran to address the international community's growing concerns about its nuclear program."
Germany expressed "great concern". British Foreign Secretary David Miliband said: "Instead of engaging with us, Iran chooses to provoke and dissemble."
Mark Fitzpatrick, chief proliferation analyst at London's International Institute for Strategic Studies, said the move was a show of Iranian "braggadocio" which made an attack on its nuclear sites more likely.
Israel, assumed to have the Middle East's only nuclear arsenal, has hinted at the possibility of attacking Iranian facilities if it deems diplomacy at a dead end. Washington has publicly opposed the idea of Israeli pre-emptive strikes.
"I am sad to say that Iran's announcement makes a military attack on the facilities more likely. If so, it will be a more target-rich environment," Fitzpatrick said.
The new enrichment facilities would be on the same scale as Iran's main enrichment complex at Natanz and work on the plants would begin within two months, state broadcaster IRIB said.
Iran's atomic energy organisation chief, Ali Akbar Salehi, said they would be built so that they would be protected from any military attack, for example in the "hearts of mountains".
"The reason is that the Islamic republic of Iran has decided not to halt its enrichment activities even for one moment," Salehi said.
The International Atomic Energy Agency angered Iran on Friday when it censured the Islamic Republic for secretly building a second uranium enrichment plant in a mountain bunker near Qom, in addition to the one in Natanz.
"This is the reaction to the resolution which was bound to happen," a senior diplomat close to the IAEA said, adding that it was unclear how much of it was bluff or a real plan.
Ahmadinejad said Iran should aim to produce 250-300 tonnes of nuclear fuel a year and that new, faster centrifuges should be used to reach that target. He did not give a time frame.
"We have a friendly approach towards the world but at the same time we won't let anyone harm even one iota of the Iranian nation's rights," he said.
IRIB said the location of five of the 10 new plants had already been decided and that work on these should start within two months. At the same time, the Atomic Energy Organisation should find suitable locations for the other five.
It did not say when the plants would be completed.Analysts were sceptical whether sanctions-bound Iran, which has problems obtaining materials and components abroad, would be able to equip and operate 10 new plants.
"They don't have the capacity. They'd like to have it," said David Albright, president of the Institute for Science and International Security in Washington.
"It's a crazy idea," he added. "But you have to look under the surface. They're mad about the IAEA resolution...It's playground behaviour in a way."
Enriched uranium can be used as fuel for nuclear power plants and, if refined much further, provide material for bombs.
Ahmadinejad said the government last week studied the issue of producing nuclear fuel enriched to 20 percent, IRIB reported, compared with the level of 3.5 percent it has now. A nuclear bomb would require an enrichment level of over 80 percent.
ISNA news agency gave a different version, saying the issue would be discussed by the government this week.
Estimates vary, but proliferation experts say 1,000-1,700 kg of low-enriched uranium, if converted into high-enriched uranium, would be enough to make a bomb.
Western powers backed a U.N.-drafted nuclear fuel deal in October that was designed to allay international concern about Iran's atomic activities, but Tehran declined it.
Earlier on Sunday, Iranian lawmakers urged the government to prepare a plan to reduce cooperation with the IAEA over its rebuke.
"Because of world powers' hasty behaviour, the government should submit its plan over reducing Iran's cooperation level with the agency," MPs said in a statement.
Parliament can oblige the government to change the level of cooperation with the IAEA, as it did in 2006 after the agency in Vienna voted to report Iran to the U.N. Security Council. (Reuters)