As the deadline looms for Iran to prove that it has no secret plans to build an atomic bomb, Iranians are being forced to make a choice.
Will Iran guarantee to the International Atomic Energy Agency (IAEA) that its advanced nuclear program is for energy only, and permit snap, go-anywhere inspections? Or will Iran decide - as it eyes nuclear Israel, Pakistan, and India, and with US troops now deployed along its borders in three directions - that it must have a nuclear deterrent that also appeals to national pride?
"We have not reached the fork in the road that tells us if this is for military or civilian use," says a senior Western diplomat here. "But if it is going for a bomb, Iran is entering the 'danger zone.' Once you have it, you are secure. But when you are close, this is a moment of great vulnerability. This is when there could be a preemptive war that would have broad support. It's the Osirak Syndrome," he says, referring to the nearly built Iraqi reactor Israeli jets destroyed in 1981.
Iran must make its choice by Oct. 31, a US-backed deadline adopted last Friday by the IAEA in the wake of heavy US lobbying to censure Iran for noncompliance. It comes as the IAEA delves deeper into a series of nuclear issues with Iran - such as misreporting its activities and the presence of highly enriched uranium - that experts say point toward the existence of a clandestine weapons program.
The IAEA resolution, adopted unanimously by the 35-nation governing board, calls on Iran to "remedy all failures," to open all sites, agree to environmental sampling, and to suspend its enrichment programs to show good will.
Failure to meet the deadline could spark a chain of events leading to the UN Security Council, which could impose sanctions and prevent all nations from assisting Iran's nuclear programs.
Iranian officials declare repeatedly that Iran's intentions are peaceful, and that it is Iran's right, as a signatory to the nuclear Non-Proliferation Treaty (NPT), to pursue nuclear science and power.
"We don't need atomic bombs, and based on our religious teaching, we will not pursue them," the reform-minded President Mohammad Khatami, who has long called for a "dialogue of civilizations" and a nuclear-free zone in the Middle East, said earlier this week. "But at the same time, we want to be strong, and being strong means having knowledge and technology."
That denial does not always square with the view on the street, where many reformers and conservatives - normally at each other's throats, politically - see nuclear weapons as a matter of patriotism and national pride, befitting a regional superpower. "No matter what they tell you, most Iranians want the bomb," says a middle-aged Iranian professional, who asked not to be named.
The disparate views point to internal disagreements over how Iran should exercise its power in the future, and how the Islamic Republic, which was closed off to much of the West for years after the 1979 Islamic revolution, should relate to the rest of the world.
Though Iran is a member of the NPT, like the United States and most other nations, it has not signed the far stricter Additional Protocol, which allows intrusive inspections. Israel never signed the NPT; Pakistan and India are not members either - facts that cause critics in Iran to speak of a double standard.
The IAEA ultimatum is a "historical opportunity for our nation to clarify its relations with the international bullies and blackmailers," the hardline Jomhuri-ye Eslami newspaper wrote. "This has proven the bitter truth that, in today's world, the only way for countries wishing to maintain their independence and survive is to become powerful."
The conservative Keyhan wrote of a "calculated conspiracy" to topple the Islamic regime, and pointed to NPT membership as a "weak point." Withdrawal from the safeguard mechanism, the paper wrote, is a "necessary move for Iran and any delay could entail irreparable and dangerous consequences."
Washington, which considers Iran to be part of its "axis of evil," warned this week that it will use "every tool" to prevent the spread of weapons of mass destruction. While testifying on Syria to a House subcommittee on Tuesday, John Bolton, the State Department's top arms-control official, made a broad warning that echoed in Iran.
"We believe the Additional Protocol should be a new minimal standard for countries to demonstrate their nonproliferation bona fides," Mr. Bolton said. The US argues that oil- and gas-rich Iran has no need of nuclear energy.
Iranian officials, despite storming out of the Vienna meeting, and then warning that Iran could pull out of the NPT, this week reaffirmed that Iran is "fully committed" to its NPT responsibilities.
But apparent threats from Washington make conservative Amir Mohebian, political editor of the Resalat newspaper, and many other Iranians, bristle - and more reluctant to sign the protocol.
"What they are saying is, 'We consider you an evil country, and you must sign it, because we don't trust you,' but it is a pretext for doing in Iran what they did in Iraq," says Mr. Mohebian, who states Iran is not pursuing weapons. "Before the  revolution, it was the Americans who gave this plan of nuclear power plants to Iran, while the population was half what it is today."
Still, a string of IAEA reports makes clear that Iran has not fulfilled all its safeguard duties. Iran has offered explanations, though the IAEA is still examining questions about previously undeclared uranium-enrichment facilities, the presence of particles of two types of highly enriched uranium, and "considerable modifications" to the suspect workshop of the Kalaye Electric Company in Tehran.
Iran initially put off IAEA testing at the Kalaye site; when samples were finally taken, diplomatic sources say, IAEA teams found the floor had been relaid with yard-deep concrete, switches had been removed, and the facility repainted.
Russia is building Iran an $800 million nuclear-power reactor at Bushehr - a sore point in US-Russian relations - and is close to signing a deal that would return all spent fuel provided by Moscow, so it cannot be further processed by Iran.
But beyond that, Iran says it aims to have control over the complete nuclear-fuel cycle, and so is pursuing several different, expensive methods on its own.
There are plans for a heavy water reactor to break ground next year at Arak, and a large pilot enrichment project that may involve a cascade of up to 1,000 centrifuges is well under way at Natanz. Laser enrichment is also a possibility. All of these could, besides civilian use, yield weapons-grade material.
Some say the Natanz site was never meant to be secret. "It's big, it's vulnerable. Why put it in the desert, where anybody can see it rising before their eyes?" says the senior Western diplomat. "Even if Natanz were shut down or destroyed, this does not solve anything. What is important is the technical knowledge."
While noting an "increased degree of cooperation" with Iran, the IAEA Aug. 26 report points out delays, inconsistent explanations, and a number of "important" issues that "require urgent resolution."
"There has been a pattern of deception, obfuscation, delay, and changing of the facts," says a Western diplomat. "And while constantly declaring it is providing full cooperation, the reports of the IAEA show that simply has not been the case. This is one reason the international community has lost patience."
Such continuing uncertainty creates new risk, analysts say, by offering ammunition to Iran critics. "If I were Iranian, my only goal would be to have the bomb as soon as possible - it makes strategic sense, Iran is proud, and it is seen as somehow legitimate, since Israel and Pakistan have it," says anotherWestern diplomat.
"The deadline is good, it puts Iran into a corner, but even if Iran opens everything, there will still be uncertainties," the diplomat says. "In this climate, any claims can be made. Iran is opening itself up for people to make connections, on issues of supporting Al Qaeda, and nuclear weapons, that may not exist."
Still, Iran may be learning from others' mistakes. "The leadership has been very mature on this," says an Asian diplomat. "They learned the lesson of Pakistan," which in 1965 said, "We will eat grass or leaves.... But we will get [a bomb] of our own." When India tested a bomb in 1974, Pakistan too was placed under embargo. Even before Pakistan's program bore fruit, the US in 1979 temporarily cut all aid as punishment.
"There will be a temptation here, and such a thing can uplift the morale of a nation, which is so low right now," he adds. "There were celebrations in India and Pakistan when they did it. Poor people were dancing in the street."