Patrick Clawson, an expert on Iran who is the deputy director for research at the Washington Institute for Near East Policy, a conservative think tank, told me that the “biggest moment” of tension has yet to arrive: “How does the United States keep an Israeli decision point—one that may come sooner than we want—from being reached?” Clawson noted that there is evidence that Iran has been slowed by technical problems in the construction and operation of two small centrifuge cascades, which are essential for the pilot production of enriched uranium. Both are now under I.A.E.A. supervision. “Why were they so slow in getting the second cascade up and running?” Clawson asked. “And why haven’t they run the first one as much as they said they would? Do we have more time?

“Why talk about war?” he said. “We’re not talking about going to war with North Korea or Venezuela. It’s not necessarily the case that Iran has started a weapons program, and it’s conceivable—just conceivable—that Iran does not have a nuclear-weapons program yet. We can slow them down—force them to reinvent the wheel—without bombing, especially if the international conditions get better.”

Clawson added that Secretary of State Rice has “staked her reputation on diplomacy, and she will not risk her career without evidence. Her team is saying, ‘What’s the rush?’ The President wants to solve the Iranian issue before leaving office, but he may have to say, ‘Darn, I wish I could have solved it.’ ”

Earlier this year, the government of Israeli Prime Minister Ehud Olmert created a task force to coördinate all the available intelligence on Iran. The task force, which is led by Major General Eliezer Shkedi, the head of the Israeli Air Force, reports directly to the Prime Minister. In late October, Olmert appointed Ephraim Sneh, a Labor Party member of the Knesset, to serve as Deputy Defense Minister. Sneh, who served previously in that position under Ehud Barak, has for years insisted that action be taken to prevent Iran from getting the bomb. In an interview this month with the Jerusalem Post, Sneh expressed skepticism about the effectiveness of diplomacy or international sanctions in curbing Iran:

The danger isn’t as much Ahmadinejad’s deciding to launch an attack but Israel’s living under a dark cloud of fear from a leader committed to its destruction. . . . Most Israelis would prefer not to live here; most Jews would prefer not to come here with families, and Israelis who can live abroad will . . . I am afraid Ahmadinejad will be able to kill the Zionist dream without pushing a button. That’s why we must prevent this regime from obtaining nuclear capability at all costs.

A similar message was delivered by Benjamin Netanyahu, the Likud leader, in a speech in Los Angeles last week. “It’s 1938 and Iran is Germany. And Iran is racing to arm itself with atomic bombs,” he said, adding that there was “still time” to stop the Iranians.

The Pentagon consultant told me that, while there may be pressure from the Israelis, “they won’t do anything on their own without our green light.” That assurance, he said, “comes from the Cheney shop. It’s Cheney himself who is saying, ‘We’re not going to leave you high and dry, but don’t go without us.’ ” A senior European diplomat agreed: “For Israel, it is a question of life or death. The United States does not want to go into Iran, but, if Israel feels more and more cornered, there may be no other choice.”

A nuclear-armed Iran would not only threaten Israel. It could trigger a strategic-arms race throughout the Middle East, as Saudi Arabia, Jordan, and Egypt—all led by Sunni governments—would be compelled to take steps to defend themselves. The Bush Administration, if it does take military action against Iran, would have support from Democrats as well as Republicans. Senators Hillary Clinton, of New York, and Evan Bayh, of Indiana, who are potential Democratic Presidential candidates, have warned that Iran cannot be permitted to build a bomb and that—as Clinton said earlier this year—“we cannot take any option off the table.” Howard Dean, the chairman of the Democratic National Committee, has also endorsed this view. Last May, Olmert was given a rousing reception when he addressed a joint session of Congress and declared, “A nuclear Iran means a terrorist state could achieve the primary mission for which terrorists live and die—the mass destruction of innocent human life. This challenge, which I believe is the test of our time, is one the West cannot afford to fail.”

Despite such rhetoric, Leslie Gelb, a former State Department official who is a president emeritus of the Council on Foreign Relations, said he believes that, “when push comes to shove, the Israelis will have a hard time selling the idea that an Iranian nuclear capability is imminent. The military and the State Department will be flat against a preëmptive bombing campaign.” Gelb said he hoped that Gates’s appointment would add weight to America’s most pressing issue—“to get some level of Iranian restraint inside Iraq. In the next year or two, we’re much more likely to be negotiating with Iran than bombing it.”