It has been two years since the United Nations demanded that Iran suspend it's enrichment of uranium so that a thorough review of its nuclear program could take place under the auspices of the IAEA.

Since then, Iran has installed more than 3,000 centrifuges at its facility in Nantanz to convert uranium to either nuclear fuel to power a reactor or highly enriched uranium to build a bomb. This despite 3 different sets of sanctions given out by the Security Council.

Now the Iranians are making a giant leap in capability by seeking to double the number of operational centrifuges at Nantanz:

Iran has begun installing 6,000 new centrifuges at its uranium enrichment plant in Natanz, state television quoted President Mahmoud Ahmadinejad as saying Tuesday.

The U.S. immediately criticized the announcement as an example of Iran's continued defiance of international demands that it suspend uranium enrichment, which can produce fuel for a nuclear reactor or fissile material for a weapon.

"Today's announcement reflects the Iranian leadership's continuing violation of international obligations and refusal to address international concerns," said Gregory Schulte, the U.S. representative to the Vienna-based International Atomic Energy Agency. Iran already has about 3,000 centrifuges operating at its underground nuclear facility in Natanz, and the U.N. has passed three sets of sanctions against Iran for its refusal to suspend uranium enrichment.

Tehran insists its nuclear program is focused on the peaceful production of energy, not the development of weapons as claimed by the U.S. and many of its allies.

"Iran has not only failed to suspend enrichment, but has chosen to ignore the will of the international community by announcing the installation of new centrifuges," said a spokesman for Britain's Foreign Office on condition of anonymity in line with policy.