By DAVID E. SANGER and HELENE COOPER
Appearing before reporters in Pittsburgh, Mr. Obama said that the Iranian nuclear program “represents a direct challenge to the basic foundation of the nonproliferation regime.” President Nicolas Sarkozy of France, appearing beside Mr. Obama, said that Iran had a deadline of two months to comply with international demands or face increased sanctions.
“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 entire international community,” Prime Minister Gordon Brown of Britain said, standing on the other side of Mr. Obama. “The international community has no choice today but to draw a line in the sand.”
The extraordinary and hastily arranged joint appearance by the three leaders — and Mr. Obama said that Chancellor Angela Merkel of Germany had asked him to convey that she stood with them as well — adds urgency to the diplomatic confrontation with Iran over its suspected ambition to build a nuclear weapons capacity. The three men demanded that Iran allow the International Atomic Energy Agency to conduct an immediate inspection of the facility, which is said to be 100 miles southwest of Tehran.
American officials said that they had been tracking the covert project for years, but that Mr. Obama decided to disclose the American findings after Iran discovered, in recent weeks, that Western intelligence agencies had breached the secrecy surrounding the complex. On Monday, Iran wrote a brief, cryptic letter to the International Atomic Energy Agency, saying that it now had a “pilot plant” under construction, whose existence it had never before revealed.
In a statement from its headquarters in Vienna on Friday, the atomic agency confirmed that it had been told on Monday by Iran that “a new pilot fuel enrichment plant is under construction in the country.” The agency said it had requested more information about the plant and access to it as soon as possible. “The agency also understands from Iran that no nuclear material has been introduced into the facility,” the statement said.
On Friday, ISNA, an Iranian news agency, quoted an “informed source” as confirming the existence of the second uranium-enrichment site, describing it as similar to Iran’s known enrichment facility at Natanz.
Iran’s president, Mahmoud Ahmadinejad, said nothing about the plant during his visit this week to the United Nations, where he repeated his contention that Iran had cooperated fully with inspectors and that allegations of a nuclear weapons program are fabrications.
The newly discovered enrichment plant is not yet in operation, American officials said, but could be by next year.
Mr. Obama’s announcement will probably overshadow much of the meeting of the Group of 20, whose leaders have gathered to plan the next steps in combating the global financial crisis. Instead, here and during the opening of the United Nations in New York, senior officials from several of the countries were pulled aside for briefings on the new intelligence and for strategy sessions about the first direct talks with Iran in 30 years — set for Thursday — that will include the United States.
American officials said they expected the announcement to make it easier to build a case for international sanctions if Iran blocked inspectors or refused to halt its nuclear program.
“They have cheated three times,” one senior administration official with access to the intelligence said of the Iranians late on Thursday evening. “And they have now been caught three times.”
The official was referring to information unearthed by an Iranian dissident group that led to the discovery of the underground plant at Natanz in 2002, and evidence developed two years ago — after Iran’s computer networks were pierced by American intelligence agencies — that the country had secretly sought to design a nuclear warhead. American officials believe that effort was halted in late 2003.
After months of talking about the need for engagement, Mr. Obama appears to have made a leap toward viewing tough new sanctions against Iran as an inevitability. He avoided President Ahmadinejad at the United Nations this week, despite his having said repeatedly that he would seek dialogue with Iranian leaders. Instead, Mr. Obama spent much of his time in New York pressing the case, particularly to Russia and China, for sterner Security Council measures to rein in Tehran’s nuclear ambitions.
For years, American intelligence officials have searched for a site where Iran could enrich uranium in secret, far from the inspectors who now regularly monitor activity at Natanz. A highly classified Bush-era intelligence report identifies more than a dozen suspected nuclear sites around the country — some for building centrifuges and other equipment, others for designing weapons or testing explosives.
Administration officials could not immediately say if the new site, built inside a mountain near the ancient city of Qum, one of the holiest Shiite cities in the Middle East, is on that list.
American officials said late Thursday that they believe the plant was designed to hold about 3,000 centrifuges, which enrich uranium for nuclear power plants — or, with additional enrichment, for bombs. That would be enough centrifuges to manufacture about one bomb’s worth of material a year, though it is unclear whether any of the centrifuges have been installed or turned on.
The I.A.E.A. statement said Iran had told the agency the new plant would enrich uranium to a level of 5 percent —high enough for nuclear fuel, but not nearly enough to make the fissile material for an atomic bomb. Iran assured the agency in its letter that “further complementary information will be provided in an appropriate and due time,” the I.A.E.A. said.
However, Mr. Obama said on Friday, “The size and type of the facility is inconsistent with that of a peaceful facility.”
Mr. Obama was first briefed on Iran’s project before he became president, as part of the detailed intelligence reports provided by the then-director of national intelligence, Mike McConnell. Mr. Obama has received updated intelligence on it “several times,” one senior aide said Thursday evening.
In advance of Friday morning’s announcement, Mr. Obama sent top intelligence officials to brief the atomic agency’s chief inspector, Olli Heinonen. Other American diplomats and intelligence officials shared their findings with China, Russia and Germany, all important players in the negotiations with Iran.
Earlier this week, Mr. Obama’s discussions with President Hu Jintao of China on Tuesday and his meeting with President Dmitri A. Medvedev of Russia on Wednesday focused largely on Iran, administration officials said. During his meeting with Mr. Medvedev in particular, Mr. Obama pressed his case, expressing pessimism that talks scheduled for next week with the Iranians over the nuclear issue would yield much progress, administration officials said.
“The president made clear that while he was willing to engage, he was also clear-eyed about the prospects of that engagement,” a senior administration official said.
Mr. Obama had, by that point, made a giant step toward getting Russia more amenable to the idea of sanctions against Iran — something Moscow does not like — by announcing last week that he was replacing President George W. Bush’s missile defense with a version less threatening to Moscow. That issue, one administration official said, completely changed the dynamic during Mr. Obama’s meeting with Mr. Medvedev.
While it is unclear whether Mr. Obama briefed Mr. Medvedev about the Qum facility during that meeting at New York’s Waldorf Astoria Hotel, the two leaders nonetheless emerged with Mr. Medvedev promising, for the first time publicly, that Russia would be amenable to tougher sanctions.
One administration official said that the United States was hoping that with Russia agreeing to tougher sanctions, China would follow. Mr. Obama is planning to visit Beijing and Shanghai in early November, just around the same time that a sanctions resolution is expected to be introduced at the Security Council.
Alan Cowell contributed reporting from Paris.
