The latest estimate by US officials lines up very closely with Israel's understanding of where the Iranian nuclear program is right now.

The Hill:

Iran could build and set off a nuclear weapon within two to three years if it decided to pursue one, Defense Secretary Leon Panetta said in a television interview aired Sunday.

"The consensus is that, if they decided to do it, it would probably take them about a year to be able to produce a bomb and then possibly another one to two years in order to put it on a deliverable vehicle of some sort in order to deliver that weapon," Panetta said during a profile on CBS's "60 Minutes."

Tensions with Iran have mounted in recent months over Tehran's threat to close the Strait of Hormuz and the killing of an Iranian nuclear scientist. Iran has said its nuclear ambitions are peaceful.

Panetta, who served as director of the Central Intelligence Agency for two-and-a-half years before heading to the Pentagon, reiterated the Obama administration's position that it would do everything it could to prevent Iran from becoming a nuclear power. "If they proceed and we get intelligence that they're proceeding with developing a nuclear weapon, then we will take whatever steps are necessary to stop it," he said. Asked if that meant a possible military strike, he repeated a line oft-used by President Obama: "There are no options that are off the table."

The thinking goes, if Iran can enrich uranium to 20% - which they can do right now - they have the technogical capability to go all the way to nuclear weapons grade uranium, which is enriched to 90%. Technically, they have the ability to construct a bomb within a few months to a year - the time it would take to enrich the 20% uranium to bomb grade - as long as they have a workable design for a device and can evade detection by the UN and the west.

Delivering the nuke is another story and even Israel acknowledges that Iran is still a few years from having the capability to marry a warhead to one of their rockets.

Israel won't wait as long as America would like in order to deal with the Iranian problem. They can't afford to sit by waiting for evidence that may never be forthcoming. The decision on whether to attack will be made based on Israel's understanding of Iranian capabilities and not necessarily hard evidence that Tehran is actually constructing a weapon.