In Gardiner's war games, the conduct of Iran's nemesis, Israel, is often the hardest to predict. Are Israeli intelligence officials exaggerating when they say Iran will have mastered the technology to make nuclear weapons by next year? Will Israel stage its own attack on Iran if Washington does not? Or is it posturing in order to goad America into military action? The simulations have led Gardiner to an ominous conclusion: though the United States is now emphasizing sanctions and diplomacy as the means of compelling Tehran to stop enriching uranium, an Israeli attack on Iran's nuclear facilities could end up dragging Washington into a war. "Even if Israel goes it alone, we will be blamed," says Gardiner. "Hence, we would see retaliation against U.S. interests."

How far will Israel go to keep Iran from getting the bomb? The question gained new urgency this month when Israeli warplanes carried out a mysterious raid deep in Syria and then threw up a nearly impenetrable wall of silence around the operation. Last week opposition leader Benjamin Netanyahu chipped away at that wall, saying Israel did in fact attack targets in Syrian territory. His top adviser, Mossad veteran Uzi Arad, told NEWSWEEK: "I do know what happened, and when it comes out it will stun everyone."

Official silence has prompted a broad range of speculation as to what exactly took place. One former U.S. official, who like others quoted in this article declined to be identified discussing sensitive matters, says several months ago Israel presented the Bush administration with reconnaissance images and information from secret agents alleging North Korea had begun to supply nuclear-related material to Syria. Some U.S. intelligence reporting, including electronic signal intercepts, appeared to support the Israeli claims. But other U.S. officials remain skeptical about any nuclear link between Syria and North Korea. One European security source told NEWSWEEK the target might have been a North Korean military shipment to Iran that was transiting Syria. But a European intelligence official said it wasn't certain Israel had struck anything at all.

While the Bush administration appears to have given tacit support to the Syria raid, Israel and the United States are not in lockstep on Iran. For Israel, the next three months may be decisive: either Tehran succumbs to sanctions and stops enriching uranium or it must be dealt with militarily. (Iran says its program is for peaceful purposes only.) "Two thousand seven is the year you determine whether diplomatic efforts will stop Iran," says a well-placed Israeli source, who did not want to be named because he is not authorized to speak for the government. "If by the end of the year that's not working, 2008 becomes the year you take action."

In Washington, on the other hand, the consensus against a strike is firmer than most people realize. The Pentagon worries that another war will break America's already overstretched military, while the intelligence community believes Iran is not yet on the verge of a nuclear breakthrough. The latter assessment is expected to appear in a secret National Intelligence Estimate currently nearing completion, according to three intelligence officials who asked for anonymity when discussing nonpublic material. The report is expected to say Iran will not be able to build a nuclear bomb until at least 2010 and possibly 2015. One explanation for the lag: Iran is having trouble with its centrifuge-enrichment technology, according to U.S. and European officials.

Twice in the past year, the United States has won U.N. Security Council sanctions against Tehran. More measures might come up at Security Council discussions later this year, and recently French Foreign Minister Bernard Kouchner warned that European nations might impose their own sanctions. One U.S. official who preferred not to be identified discussing sensitive policy matters said he took part in a meeting several months ago where intelligence officials discussed a "public diplomacy" strategy to accompany sanctions. The idea was to periodically float the possibility of war in public comments in order to keep Iran off balance. In truth, the official said, no war preparations are underway.

There are still voices pushing for firmer action against Tehran, most notably within Vice President Dick Cheney's office. But the steady departure of administration neocons over the past two years has also helped tilt the balance away from war. One official who pushed a particularly hawkish line on Iran was David Wurmser, who had served since 2003 as Cheney's Middle East adviser. A spokeswoman at Cheney's office confirmed to NEWSWEEK that Wurmser left his position last month to "spend more time with his family." A few months before he quit, according to two knowledgeable sources, Wurmser told a small group of people that Cheney had been mulling the idea of pushing for limited Israeli missile strikes against the Iranian nuclear site at Natanz—and perhaps other sites—in order to provoke Tehran into lashing out. The Iranian reaction would then give Washington a pretext to launch strikes against military and nuclear targets in Iran. (Wurmser's remarks were first reported last week by Washington foreign-policy blogger Steven Clemons and corroborated by NEWSWEEK.) When NEWSWEEK attempted to reach Wurmser for comment, his wife, Meyrav, declined to put him on the phone and said the allegations were untrue. A spokeswoman at Cheney's office said the vice president "supports the president's policy on Iran."

In Iran, preparations for war are underway. "Crisis committees" have been established in each government ministry to draw up contingency plans, according to an Iranian official who asked for anonymity in order to speak freely. The regime has ordered radio and TV stations to prepare enough prerecorded programming to last for months, in case the studios are sabotaged or employees are unable to get to work. The ministries of electricity and water are working on plans to maintain service under war conditions. Supreme Leader Ayatollah Ali Khamenei has also sent envoys to reach out to European negotiators recently, in the hopes of heading off further sanctions or military action.

The question may not be whether America is ready to attack, but whether Israel is. The Jewish state has cause for worry. Iranian President Mahmoud Ahmadinejad vows regularly to destroy the country; former president Hashemi Rafsanjani, considered a moderate, warned in 2001 that Tehran could do away with Israel with just one nuclear bomb. In Tel Aviv last week, former deputy Defense minister Ephraim Sneh concurred. Sneh, a dovish member of Israel's Parliament and a retired brigadier general, took a NEWSWEEK reporter to the observation deck atop the 50-story Azrieli Center. "There is Haifa just over the horizon, Ben-Gurion airport over there, the Defense Ministry down below," he said, to show how small the country is. "You can see in this space the majority of our intellectual, economic, political assets are concentrated. One nuclear bomb is enough to wipe out Israel."

But can the Israelis destroy Iran's nuclear program? Gardiner, the war-gamer, says they would not only need to hit a dozen nuclear sites and scores of antiaircraft batteries; to prevent a devastating retaliation, they would have to knock out possibly hundreds of long-range missiles that can carry chemical warheads. Just getting to distant Iran will be tricky for Israel's squadrons of American-made F-15s and F-16s. Danny Yatom, who headed Mossad in the 1990s, says the planes would have to operate over Iran for days or weeks. Giora Eiland, Israel's former national-security adviser, now with Tel Aviv's Institute of National Security Studies, ticked off the drawbacks: "Effectiveness, doubtful. Danger of regional war. Hizbullah will immediately attack [from Lebanon], maybe even Syria." Yet Israelis across the political spectrum, including Eiland and Yatom, believe the risk incurred by inaction is far greater. "The military option is not the worst option," Yatom says. "The worst option is a nuclear Iran."

The idea of a pre-emptive strike also has popular support. When Prime Minister Ehud Olmert ordered the raid on Syria earlier this month, his approval rating was in the teens. Since then, it has jumped to nearly 30 percent. And though Olmert may not believe Israeli warplanes can get to all the targets, he might be willing to gamble on even a limited success. "No one in their right mind thinks that there's a clinical way to totally destroy the Iranian nuclear facilities," says the well-placed Israeli source. "You strike at some and set the project back. You play for time and hope Ahmadinejad will eventually fall."

Alternatively, Israel might count on Tehran to retaliate against American targets as well, drawing in the superpower. To avoid that outcome, Gardiner believes, Washington must prevent Israel from attacking in the first place. "The United States does not want to turn the possibility of a general war in the Middle East over to the decision making in Israel," he says. Does not want to, certainly—but might not have a choice.

With Rod Nordland in Jerusalem, Christopher Dickey in New York and John Barry in Washington