AND JIM TANKERSLEY, WASHINGTON AND PITTSBURGH — Dramatically heightening the international confrontation over Iran, President Obama on Friday revealed the existence of an underground uranium enrichment site that the Islamic Republic had kept secret from international inspectors for years.
Disclosure of the site -- which Tehran did not deny, but said was for peaceful purposes -- sharpened accusations that Iran is deceiving the world about its nuclear intentions.
"Iran is breaking rules that all nations must follow," Obama said in remarks at an international summit in Pittsburgh, where he described the site and said that Tehran was "threatening the stability and security of the region and the world."
Intelligence officials said the installation is buried deep inside a mountain about 100 miles southwest of Tehran, in a heavily guarded compound operated by the Revolutionary Guard.
Once operational, the facility would be capable of producing enough fuel each year to arm a nuclear warhead, according to U.S. intelligence officials who have been secretly tracking the site since at least 2006.
The disclosure, timed by the Obama administration for dramatic as well as diplomatic effect, came while Iranian President Mahmoud Ahmadinejad was in New York, where he spoke at the United Nations this week, and only days before the United States and five other nations are scheduled to resume talks with Tehran about its nuclear program.
Iran appears to have become aware that the secrecy surrounding the site had been penetrated, prompting a cryptic disclosure to the International Atomic Energy Agency, or IAEA, in a letter sent this week.
But Obama, who came into office seeking a thaw in U.S.-Iranian relations, took the unusual step of unveiling details about the secret site himself during an appearance alongside the leaders of France and Britain at the Group of 20 conference of industrialized and key developing nations in Pittsburgh.
French President Nicolas Sarkozy and British Prime Minister Gordon Brown, whose spy services worked closely with their U.S. counterparts to gather intelligence on the site, condemned Iran's conduct.
"The level of deception by the Iranian government, and the scale of what we believe is the breach of international commitments, will shock and anger the whole international community," Brown said.
"And it will harden our resolve."
Beyond escalating diplomatic tensions, the revelation raised anxiety about the potential spread of nuclear arms in the Middle East, as well as concern that Iran's program may have reached a point where it can no longer be stopped by military strike, but only delayed.
The disclosure appeared to solidify support among key nations for new sanctions on Iran. Russian President Dmitry Medvedev voiced new support for such measures this week, saying that "when all instruments have been used and failed, one can use international legal sanctions."
U.S. officials said Medvedev and Obama discussed the new Iranian facility for the first time Wednesday during a private meeting at the Waldorf-Astoria hotel in New York. Administration officials said similar details had also been shared with Chinese officials this week.
Ahmadinejad on Friday denied that Iran was breaking any international law, and sought to downplay the significance of the site, describing it as "a very ordinary facility in the beginning stages."
In a news conference at a midtown Manhattan hotel, Ahmadinejad said the plant would not be operational for 18 months, and that Iran was not required to report work on such facilities until six months before they go online.
Earlier, in an interview with Time magazine, the Iranian leader appeared to be caught off guard and angered by the disclosure. "Mr. Obama is about to say this?" he asked, before adding that Obama's disclosure "simply adds to the list of issues for which the United States owes the Iranian nation an apology."
American intelligence officials said the site would not accelerate Iran's ability to build a bomb. U.S. spy agencies believe that Tehran has not restarted work on nuclear warhead design, and remains one to five years away from producing highly enriched uranium suitable for a weapon.
Still, experts said the nature of the second enrichment facility, as well as the secrecy surrounding its development, has major implications for understanding Iran's nuclear ambitions. Several nuclear proliferation experts said the site all but erases any doubt that Iran aims to build a bomb, and raises fears that other secret sites have yet to be discovered.
The dimensions and design of the new facility near the city of Qom rule out any civilian nuclear energy purpose, U.S. intelligence officials said. The plant is large enough for only 3,000 centrifuges, a number too small to yield enough fuel for a power plant, but adequate to generate material for a bomb.