Iran put on a show of force today, essentially thumbing its nose at the world by test-firing a series of missiles, two days after the White House embarassed Tehran by revealing the location of a supposedly secret nuclear site.
Iran began its tests of short- and long-range missiles today amid shouts of "Allahu Akbar," or "God is great" in Arabic.
After the tests, the head of Iran's Revolutionary Guard Air Force said they were a success, and the country was ready to fight off attacks from any country.
"We are going to respond to any military action in a crushing manner and it doesn't make any difference which country or regime has launched the aggression," state media quoted Gen. Hossein Salami as saying.
The latest provocation from the Iranian regime comes after President Obama revealed to rest of the world last week that Iran was building a secret underground nuclear facility in the mountains near the city of Qom.
"The Islamic Republic of Iran has been building a covert uranium enrichment facility near Qom for several years," Obama said Friday, when addressing world leaders at the G-20 summit in Pittsburgh, after U.S. officials learned that Iran had disclosed the facility's existence to the International Atomic Energy Association of the facility just last week.
U.S. officials say they have known about the secret facility for a while.
"We have been following this for several years in cooperation with some of our international partners, watching and assessing what the Iranians were doing. And then when this became known, actually through the Iranians beginning to provide some information about it, we disclosed the fact and gave the information we had to the International Atomic Energy Agency," Secretary of State Hillary Clinton said on CBS's "Face the Nation."
She said that if Iran really intended the facility to be used for peaceful purposes, not weapons production, it would have been disclosed earlier.
"So I guess one has to ask, if it's for a peaceful purposes, why was it not public? Why was the fact of it not generally known instead of through our working with partners to discover it?" Clinton said.
"This is part of a pattern of deception and lies on the part of the Iranians from the very beginning with respect to their nuclear program," Defense Secretary Robert Gates said ABC's "This Week".
Gates would not say whether the United States is aware of other secret nuclear facilities in Iran.
"Well, I'm not going to -- I'm not going to get into that. I would just say that we're watching very closely," Gates said.
U.S. officials tell ABC News there are three main reasons they concluded the secret site was built to manufacture fuel for nuclear bombs.
First, it was clear from satellite imagery that a facility was being constructed underground and heavily disguised; second, it was built on a military base and protected by armed guards 24 hours a day; and third, intelligence shows it is designed to hold only about 3,000 centrifuges to enrich uranium -- not enough to fuel a civilian power plant, which would need around 50,000 centrifuges, but enough to make highly enriched uranium for a nuclear weapon.
"For the Iranians themselves this must be incredibly unsettling for them to know that Western intelligence agencies have penetrated state secrets," said Karim Sadjadpour, an Iranian expert at the Carnegie Endowment for International Peace.
Iran insists that the facility is part of a peaceful nuclear energy program, but has not explained why the site was hidden and heavily guarded, and why it was not immediately reported to international regulators.
Iranian president Mahmoud Ahmadinejad, speaking on CNN's "Larry King Live," denied the project had anything to do with nuclear weapons.
"How can he possibly accuse us of secretly engaging in an activity that did not take place?" Ahmadinejad said.
But U.S. officials greeted Ahmadinejad's denials with skepticism.
"Words are not enough. They're going to have to come and demonstrate clearly to the international community what they're up to," Clinton said.
The secretary of state said that when the representatives from the P5+1 -- including the United States, Russia, China, Great Britain, France and Germany -- meet with Iranian representatives in Geneva on Thursday, Iran must "come and demonstrate clearly to the international community what they're up to."
"We don't believe that they can present convincing evidence that it's only for peaceful purposes. But we are going to put them to the test on Oct. 1," Clinton said. "They can open up their entire system to the kind of extensive investigation that the facts call for.
"And if we don't get the answers that we're expecting and the changes in behavior that we're looking for, then we will work with our partners to move toward sanctions," she said.
It will be difficult to get meaningful new sanctions against Iran, however, because not all the members of the Security Council are likely to back the tough penalties Washington might want, Sadjadpour said.
"The Russians and Chinese are never going to sign on to very binding sanctions but they will turn up the heat very incrementally," he said.
Nonetheless, the United States is ratcheting up the pressure ahead of Thursday's meeting.
"Iran is on notice," the president said on Friday. "They are going to have to come clean and they are going to have to make a choice."
Israeli leaders, incensed that Iran's missile testing fell on Yom Kippur, the holiest of Jewish holidays, is also ratcheting up pressure on U.S. officials to take strong action.
Israeli Prime Minister Binyamin Netanyahu reportedly called American lawmakers over the weekend, urging the United States to take action against Iran for repeatedly defying the international community.
"Iran is the most serious threat today to the peace of the world and its security," Israeli Deputy Foreign Minister Danny Ayalon said.
The Israeli government has explored the idea of missile strikes against Iranian nuclear facilities, but that is an option the United States has been trying to avoid.
Even if the secret facility is struck, others could exist.
According to a U.S. intelligence official, the Iranians have a decentralized system of nuclear sites all over the country, with no "single point of failure" -- meaning that if one sight were taken out, others would still exist -- a problem American officials may be addressing for many more years to come.
ABC's Kristina Wong contributed to this report.