In standoff with Iran, no smoking gun but some strong evidence of nuclear ambitions

The accusations come almost every day from U.S. officials: Iran is seeking a nuclear weapon. Sponsoring terrorism. Killing Americans in Iraq. Intent on Israel's destruction. Yet, some officials add, its government will collapse if only given a push.

Does the U.S. have solid proof that Iran is guilty of such a long list of misdeeds? Or is the case against Iran -- and the certainty of its ill intent -- a bit fuzzy?

In the buildup to the Iraq war, the Bush administration made allegations against Saddam Hussein that polls show Americans believed but which later proved wrong.

Now, with U.S. officials leading the pressure on Iran, many Americans are weighing the evidence. Is there a smoking gun or even a smoldering one?

The United States and Iran have been enemies since the 1979 Islamic Revolution, a bitter time of black-turbaned mullahs, screaming students and blindfolded American hostages.

But both countries have changed. Brushing away the strident ideology and the distrust, what now are Iran's weapons and its intentions?

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For almost two decades, Iran pursued a secret nuclear program. It came partially to light in 2002, mostly through information from exiles, and has led to U.N. inspections, sanctions and standoff.

Iran insists its program is for civilian power generation only. The U.S. says it is for a bomb.

Many other countries agree that Iran's steps so far -- especially its enrichment of uranium and its continued secrecy -- suggest it seeks the capability to build a weapon. Those more friendly toward compromise, including Russia and China, urge Iran to be more open.

"There's no consensus that Iran's leadership has decided to build a nuclear arsenal," said David Albright, a former U.N. nuclear inspector now at Washington's Institute for Science and International Security. "There's more of a consensus that they've built a set of capabilities" that could be used for a weapon.

Even if one assumes the goal is a weapon, it is a stretch to leap from that "to the assumption you know what Iran is going to do and when," said Anthony Cordesman, a Mideast expert at the Center for Strategic and International Studies in Washington.

U.S. intelligence estimates are based mostly on the U.N. nuclear agency's findings and informed speculation, Cordesman and others say.

A new national intelligence estimate, originally due last spring, was delayed by the need to evaluate new information, the U.S. national intelligence director, Mike McConnell, said recently. But most analysts say that new information is mostly just Iran's political developments and recent U.N. findings on enrichment, already public.

Now scheduled for completion next month, the NIE -- which won't be released publicly -- will lay out the evidence and U.S. intelligence's judgment of what it shows. That judgment "is what we are wrestling through now," McConnell said.

Last February, McConnell told Congress that Iran could make a nuclear weapon by "early to mid-next decade" -- or roughly five to seven years from now.

But, he stressed, the U.S.'s information was incomplete.

The real power

President Bush suggested last month that because Iran's president is openly hostile to Israel, any Iranian possession of nuclear weapons could cause World War III.

But little is known about what Iran would do with a bomb.

While he makes headlines with his rhetoric, President Ahmadinejad faces a re-election battle in two years and his popularity is plummeting.

The real power in Iran is Ayatollah Ali Khamenei, the country's top religious and political authority whose views remain shrouded in mystery. He has backed Ahmadinejad and is deeply conservative.

But almost all Iranians believe Khamenei is far more pragmatic than the president. In plain terms, he is a believer in realpolitik, the art of balancing competing factions, both hardline and pragmatic, to maintain his own position.

"We have to keep in mind, the supreme leader is not as radical as Ahmadinejad ... he cares for the survival of the country," said Mehdi Khalaji, a visiting fellow at the Washington Institute for Near East Policy.

Khalaji said he believes Khamenei would never order an attack on Israel with a nuclear weapon because the Israeli retaliation could destroy Iran.

That is what retired Gen. John Abizaid, the former U.S. commander for the region, was likely suggesting when he said the West could live with a nuclear Iran.

But with the consequences so high, the point is hotly debated: Why would Iran seek a nuclear weapon if not to use it?

Most countries seek nuclear weapons as a way to gain regional power and influence, a whole host of analysts say. Above all, a nuclear program means international clout and deterrence against aggressors.

Of course, Khalaji cautions, even if Khamenei is pragmatic, no one knows for sure what Iran's next supreme leader might be.

Largely hostile to al-Qaida

Terror is the next accusation against Iran, and here, facts are firmer.

Iran's government does send aid to militants in neighboring countries, including Hezbollah, the group it formed in Lebanon during that country's civil war and which won support across the Middle East last summer after fighting Israel to a stalemate.

Iran also supports Hamas and Islamic Jihad, the Palestinian militants who fight against Israel in Gaza and the West Bank.

The United States calls Hamas, Hezbollah and Islamic Jihad terrorist groups. Iran, in Bush's words, is "the world's leading state sponsor of terrorism."

In the 1980s, the groups' forerunners launched deadly attacks against U.S. Marines and other Americans in Lebanon.

But the Iranian-backed groups do not now pose any direct, imminent threat to the United States, said Rohan Gunaratna, head of the International Center for Political Violence and Terrorism Research in Singapore.

"The biggest threat to the United States, its allies and friends does not come -- I repeat, does not come -- from the Iran-sponsored groups," he said. "It comes from al-Qaida."

U.S. intelligence agencies broadly agree: McConnell told Congress this year that al-Qaida remained by far America's biggest threat.

No one accuses Iran of helping al-Qaida. Instead, Shiite Iran appears largely hostile to Sunni al-Qaida, said Gunaratna.

Weapons made in Iran

The place where the U.S. accuses Iran of direct harm is Iraq. For many Americans, the accusation that Iran or Iranian-backed groups are killing U.S. troops in Iraq is a call for action.

Iran denies the Bush administration charges, but a fair number of independent analysts call the U.S. evidence strong, if circumstantial.

The basic accusation is that Iran provides money and weapons to Shiite militias in Iraq that then target American troops. The evidence the U.S. cites is the spread of powerful roadside bombs called explosively formed projectiles, or EFPs, that kill troops even in heavily armored vehicles.

U.S. military officers say they know the EFPs come from Iran because they bear Iranian markings, and because captured militants have told them so. The workmanship is so precise they could only come from a modern factory with machine tools, available in Iran but not Iraq.

Recently, even as the evidence of Iranian involvement has firmed, the number of EFP attacks has sharply declined.

U.S. Maj. Gen. James Simmons said Nov. 15 that Iran's promises to Iraq's government that it would stem the flow of weapons "appear to be holding up."

Why would Iran suddenly stop funding attacks?

There are many theories and no certainty: Perhaps Iran felt it had made the point it could be dangerous. Maybe it wanted to stay on the Iraqi government's good side. Perhaps it felt rival Sunni Muslims were so beaten down, it no longer needed to help fellow Shiites.

Or perhaps Iran worried the U.S. might retaliate unless it eased off.

A surviving regime

U.S. officials have been cautious about the chances of "regime change" in Iran, although a handful of Bush administration figures have called it an option.

There are numerous signs Iranians dislike their current government. Iran's young, well-educated population sometimes chafes at authoritarian rule. The country has an inefficient economy, made worse by Ahmadinejad's blunders.

But Iran's clerical regime "has survived everything short of the plague" in its 28 years, said Suzanne Maloney, a senior fellow at the Saban Center for Middle East Policy in Washington.

And no coherent, organized opposition has ever emerged.

Khalaji is blunt: Ahmadinejad may be unpopular and "very fragile." But he says: "The regime is not vulnerable at all."