Iran turned up the heat this week on still-simmering concerns about its atomic aspirations. It crowed that its 1,000-megawatt Bushehr nuclear-power plant would be "online" as early as this spring, putting in place another important building block of its nuclear program.

That sort of news can't help but rattle the steadiest of nerves, no matter what the (narrowly focused) US National Intelligence Estimate on Iran's nuclear-weapons program said about the current state of affairs.

Seemingly not swayed one iota by the NIE's conclusions, you have to wonder if Israel - the country most threatened by an Iranian nuclear (weapons) breakout - might take matters into its own hands.

It has done so twice before - and the time may be here again.

In a 1981 dawn raid lasting less than 90 seconds, Israeli Defense Force fighters attacked the nearly completed 40-megawatt Iraqi Osirak nuclear-reactor complex, setting back Saddam's ability to produce fissile material for nukes.

And again last September, the IDF allegedly struck a nascent Syrian nuclear program, which possibly was benefiting from outside help, in a preventive airstrike that may have also been meant as a warning to Iran of unpleasant things to come.

But why strike now?

Well, within about a year of Bushehr becoming operational, some of its spent nuclear fuel could be stripped of enough plutonium to produce a handful of nuclear weapons if the rods aren't returned to their owner/provider, Russia.

Because the production of fissile material is the long pole in the nuclear-weapons tent, the diversion of material at Bushehr is potentially as big a problem as the 3,000 centrifuges that Iran has whirring at supersonic speeds, enriching uranium.

Attacking Bushehr - like Osirak - before it comes online would not only stop it from being used to produce bomb material, but would also prevent radiation from the reactor being spewed into the atmosphere after a strike.

Also possibly spurring Israeli Prime Minister Ehud Olmert to put the IDF into action is other recent news: Iran is reportedly buying the highly capable Russian S-300 air-defense system to bolster the Tor-M1 surface-air missile systems Moscow supplied last year.

The Iranians purchased the Tor-M1 to prevent a modern-day Iranian version of Israel's successful Osirak strike. The lethal S-300s - likely a response to the Syrian strike - will enhance Iran's ability to protect its nuclear sites scattered around the country.

(Curious the extent to which Iran is willing to go to protect its so-called "peaceful" nuclear program, isn't it?)

But despite these reasons for giving a go-ahead for an attack on Bushehr before it's up and running, dealing militarily with Iran's nuclear program is a lot more complex than just that.

While Bushehr is a key element of the program because of its ability to produce large amounts of bomb-worthy fissile material (i.e., plutonium) for weapons use, it isn't the be-all and end-all of that program.

To cripple Iran's nuclear program, the IDF would have to hit other major nuclear sites: The Natanz uranium-enrichment plant, the Arak heavy-water facility and the Isfahan uranium-conversion complex - plus possibly tens of other nuclear-related sites.

But while some facilities like Natanz are "hardened," well-protected by air defenses and often buried as deep as 70 feet down, IDF fighters could hammer them using GPS/laser-guided and penetration weapons such as the American JDAM.

There's also the tyranny of distance. Iran is a lot farther from Israel than Iraq - and the targets aren't clustered like they were at Osirak. They're spread across Iran - a country nearly four times California's size.

Even a surprise IDF air raid would likely be known to others such as the United States, which "owns" the airspace in the Middle East and the Persian Gulf with its vast array of land, sea and air sensors.

(Of course, it is always possible Israel's small fleet of cruise-missile-capable, Dolphin-class diesel submarines, deployed to the Persian Gulf, could play a role in a strike, especially against Bushehr in southern Iran.)

A strike would bring Iranian retaliation, including terrorist attacks by Tehran's allies, such as Hezbollah, as well as missile strikes against large Israeli cities. By association, US interests could come into Iran's crosshairs.

The new year will likely bring more unwelcome news about Iran's nuclear program as it cascades toward a weapons option. It will also be a fateful year for Israel, one that may require action - no matter what the latest NIE says.

Peter Brookes is a Heritage Foundation senior fellow and former US deputy assistant secretary of defense.