TEHRAN (Reuters) – Iran announced plans to build 10 new uranium enrichment plants in a major expansion of its atomic program, just two days after the United Nations 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 program 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 organization 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 metric tons of nuclear fuel a year and that new, faster centrifuges should be used to reach that target.