All eyes on Israel: Will it act against world's best interest?

Secretary of Defense Leon Panetta is refreshingly frank, sometimes stunningly so. He outdid himself on a trip to Europe last week, telling a Washington Post columnist that he's worried Israel will attack Iran in April, May or June.

Some may surmise the secretary spoke out of turn, or was just trying to raise the heat on Tehran. But the straightforward Panetta meant what he said. And if he's worried about a possible Israeli attack this spring, Americans should be worrying, too.

All the more so, since U.S. officials believe that Israel may give Washington no warning, even though an Israeli strike could cause big trouble for the United States.

Unfortunately, the American public isn't worrying, because the immediacy of the issue hasn't been evident. Tough talk about Iran has become a mainstay in this election year, with Republican candidates competing to tout military action against Tehran.

President Obama, too, has insisted all options are on the table to prevent Iran from getting nuclear weapons. But the administration is focused on ratcheting up an unprecedented level of global sanctions and economic pressures on Tehran.

Many have dismissed the rhetoric from Israel as little more than an adjunct to that pressure. Not so.

There is another reason Americans have been slow to grasp that an Israeli attack may be coming. U.S. and Israeli officials concur that, while Iran is developing the capability to build nuclear weapons, it hasn't yet decided to do so.

"The consensus is, if they decided to do it, it would probably take them about a year to be able to produce a bomb," Panetta said on CBS's "60 Minutes" last week. It would take another one to two years to put a weapon on a delivery vehicle.

In other words, the administration believes there is still sufficient time to squeeze Iran through diplomacy and sanctions. Top U.S. officials from President Obama down have been trying to impress on their Israeli counterparts the need to operate in tandem.

Panetta regularly repeats a call for U.S.-Israeli cooperation. As he put it recently on CBS's "Face the Nation": "We have common cause here. And the better approach is for us to work together."

Yet U.S. officials now believe Israel may make the decision to act on its own.

Israeli leaders insist time is running out because Iran is moving facilities into mountain bunkers that can't be destroyed by air strikes.

Barak, who with Israeli Prime Minister Benjamin Netanyahu has been a strong advocate of a military strike, says Israel must consider "an operation" before Iran reaches that point.

No doubt, Israel would prefer that the United States do the bombing, but the potential consequences of a strike are so fraught, and the benefits so uncertain, that the administration isn't ready to make that decision.

That may not stop the Israelis, who, unlike the Americans, see Iran as an existential threat.

So here's why Americans should be worried about a possible spring strike on Tehran:

One: There is broad agreement among top U.S. and Israeli security experts that an Israeli strike would not destroy Iran's nuclear program, which is scattered in several locations, some underground.

So why take such a huge risk, if the program will remain operational? As I was told by one Israeli security expert, "If a strike will only set the program back a couple of years, it makes more sense to do the same thing through covert means."

Two: Despite such a small reward, the negative consequences could be enormous. Israel may be willing to risk rocket and missile attacks from Hamas and Hezbollah. But a strike would probably boomerang by increasing Iran's determination to build a weapon, while increasing support for the regime at home.

Even if Iran didn't, or couldn't, close the Strait of Hormuz, oil prices would spike, further hurting the global economy. The entire Mideast region would be further destabilized. And for what, if Iran's nuclear program was only temporarily set back?

Three: Even if Israel attacks on its own, the United States will be blamed, with repercussions for U.S. forces in the region, and in Afghanistan. "If the Israelis made that decision," Panetta told "Face the Nation," "we would have to be prepared to protect our forces in that situation. And that's what we'd be concerned about."

Four: If Israel goes it alone, without warning its closest ally, what does that say about the state of the alliance? Is this the way Israel would treat an American ally that aids and backs it to the max?

"The most important thing is to keep the international community unified," Panetta told the Associated Press on Friday.