We know the U.S. does not want Israel to stage a unilateral attack against Iran. Bad things could happen, including: 1. it could touch off a regional conflagration; 2. oil prices could spike to over $200 a barrel; 3. the tepid economic recovery the U.S. is experiencing would nosedive; 4. no one can know the full extent of Iran's retaliatory response.
Besides, for Iran's sheer size - it is larger than Iraq and Afghanistan, combined - and the way its nuclear facilities are dispersed from one end of the country to the other, there is serious doubt that an Israeli strike would be successful. More than likely, all we would get is a truckload of problems, and no solutions.
This is geopolitical bullying at its worst: Israel is 1/100th the size of Iran with 1/10th the population. Yet, it seeks to impose its will on the Iranian people. Iran is not compelled by any logic nor law or nature to take this.
When Israel took out Saddam's Osiri nuclear plant in Iraq, Saddam did nothing. Israel followed with an attack on Syria's nuclear; its President Assad made the same mistake. Both leaders refused to respond to Israel's naked aggression, presumably because they feared a fight they might lose. Saddam lost his nation, anyway. Likewise, Assad is on the ropes in Syria.
The French have a saying: "a bon chat (shah), bon rat (rah)" - to a good cat, a good rat. Or, as Sonny Corleone would say, "They hit us, so we hit 'em back." Israel and Iran should both take heed.
So, why is America telling on Israel, anyway? Some say it is part of a good-cop/bad-cop routine. Perhaps. Others suggest that by exposing Israel's intention, Israel might be less likely to take this risk.
The bottom line: America believes an Israeli strike will not only fracture the fragile sanctions regime President Obama seeks to fashion against Iran, but it will drag the U.S. into another disastrous war.
And what of the Israeli people? Do they want their leaders bombing Iran - a strike that could unleash the wrath of Iran's sophisticated missile system? Make no mistake: Iran is not a backward Muslim nation. Just last week, they launched a satellite into orbit around the Earth. That said, Israelis in Tel Aviv, Haifa, and Jerusalem must wonder that a strike on Iran might bring the skies down on their heads. A bon chat, bon rat.