Ali Akbar Salehi, head of Iran's Atomic Energy Organization, writes a note as he listens to a journalist during a news conference in Tehran on Sept. 29. (Morteza Nikoubazl/Reuters)

Iran approved plans Sunday to build 10 industrial scale uranium enrichment facilities, a dramatic expansion of the program in defiance of UN demands that it halt enrichment and a move that is likely to significantly heighten tensions with the West.

The decision comes only days after the UN nuclear watchdog agency censured Iran over its program and demanded it halt the construction of a newly disclosed enrichment facility.

The West has signalled it is running out of patience with Iran's continuing enrichment and its balking at a UN deal aimed at ensuring Tehran cannot build a nuclear weapon in the near-term future. The United States and its allies have hinted at new UN sanctions if Iran does not respond.

The White House said the move "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.

"Time is running out for Iran to address the international community's growing concerns about its nuclear program," White House press secretary Robert Gibbs said.

British Foreign Secretary David Miliband described Iran's move as a provocation.

"This epitomizes the fundamental problem that we face with Iran," he said. "We have stated over and again that we recognize Iran's right to a civilian nuclear program, but they must restore international confidence in their intentions. Instead of engaging with us, Iran chooses to provoke and dissemble."

On Friday, the UN's International Atomic Energy Agency issued a strong rebuke of Iran over enrichment, infuriating Tehran. Parliament speaker Ali Larijani threatened on Sunday to reduce co-operation with the IAEA.

"Should the West continue to pressure us, the legislature can reconsider the level of Iran's co-operation with the IAEA," Larijani told parliament in a speech carried live on state radio.

Vice-President Ali Akbar Salehi, who is also Iran's nuclear chief, said Sunday's decision was "a firm message" in response to the IAEA. He told state TV that the agency's censure was a challenge aimed at "measuring the resistance of the Iranian nation."

Any new enrichment plants would take years to build and stock with centrifuges. But the ambitious plans were a bold show by Iran that it is willing to risk further sanctions and won't back down amid a deadlock in negotiation attempts.

Iran currently has one operating enrichment facility, at the central town of Natanz, which has churned out around 1,500 kilograms of low-enriched uranium over the past years — enough to build a nuclear weapon if Iran enriches it to a higher level.

Iran says it has no intention of doing so, insisting its nuclear program aims only to generate electricity.

The revelation of a second, previously unannounced facility, under construction for years at Fordo near the holy city of Qom, raised accusations from the U.S. and its allies that Iran was trying to expand enrichment in secret, out of inspectors' sight. Iran denied the claim.

On Sunday, a cabinet meeting headed by President Mahmoud Ahmadinejad ordered the Atomic Energy Organization of Iran to begin building five uranium enrichment plants at sites that have already been studied and propose five other locations for future construction within two months, the state news agency IRNA reported.

All would be at the same scale as Natanz.

The new sites are to be built inside mountains to protect them from possible attacks, said Salehi. They will also use a new generation of more efficient and more productive centrifuges that Iran has been working to construct, he and Ahmadinejad said.

In Vienna, spokeswoman Gillian Tudor said the IAEA would have no comment on Tehran's announcement.