But if diplomacy fails, the world should be prepared for an Israeli attack on Iran's suspected nuclear weapons facilities. As Adm. Michael Mullen, the chairman of the U.S. Joint Chiefs of Staff, recently acknowledged: "The window between a strike on Iran and their getting nuclear weapons is a pretty narrow window."

If Israel attempts such a high-risk and destabilizing strike against Iran, President Obama will probably learn of the operation from CNN rather than the CIA. History shows that although Washington seeks influence over Israel's military operations, Israel would rather explain later than ask for approval in advance of launching preventive or preemptive attacks. Those hoping that the Obama administration will be able to pressure Israel to stand down from attacking Iran as diplomatic efforts drag on are mistaken.

The current infighting among Iran's leaders also has led some to incorrectly believe that Tehran's nuclear efforts will stall. As Friday's International Atomic Energy Agency report on Iran's nuclear programs revealed, throughout the political crises of the last three months, Iran's production rate for centrifuges has remained steady, as has its ability to produce uranium hexafluoride to feed into the centrifuges.

So let's consider four past Israeli military operations relevant to a possible strike against Iran.

In October 1956, Israel, Britain and France launched an ill-fated assault against Egypt to seize control of the Suez Canal. The day before, Secretary of State John Foster Dulles grilled Abba Eban, Israel's ambassador to the U.S., about Israel's military buildup on the border with Egypt, but Eban kept quiet about his country's plans.

In June 1967, Israel initiated the Six-Day War without notice to Washington, despite President Johnson's insistence that Israel maintain the status quo and consult with the U.S. before taking action. Only days before the war began, Johnson notified Prime Minister Levi Eshkol in a personal message: "Israel just must not take preemptive military action and thereby make itself responsible for the initiation of hostilities."

On June 7, 1981, Israeli fighter-bombers destroyed the Iraqi nuclear reactor at Osirak shortly before it was to be fueled to develop the capacity to make nuclear weapons-grade plutonium. Again, Washington was not informed in advance. President Reagan "condemned" the attack and "thought that there were other options that might have been considered."

A few days later, Prime Minister Menachem Begin told CBS News: "This attack will be a precedent for every future government in Israel. ... Every future Israeli prime minister will act, in similar circumstances, in the same way."

Begin's prediction proved true on Sept. 6, 2007, when Israeli aircraft destroyed what was believed to be a North Korean-supplied plutonium reactor in Al Kibar, Syria. Four months earlier, Israeli intelligence officials had provided damning evidence to the Bush administration about the reactor, and the Pentagon drew up plans to attack it. Ironically, according to New York Times reporter David Sanger, President Bush ultimately decided the U.S. could not bomb another country for allegedly possessing weapons of mass destruction. An administration official noted that Israel's attack went forward "without a green light from us. None was asked for, none was given."

These episodes demonstrate that if Israel decides that Iranian nuclear weapons are an existential threat, it will be deaf to entreaties from U.S. officials to refrain from using military force. Soon after the operation, Washington will express concern to Tel Aviv publicly and privately. The long-standing U.S.-Israeli relationship will remain as strong as ever with continued close diplomatic, economic, intelligence and military cooperation.

Should Tehran prove unwilling to meet the September deadline and bargain away its growing and latent nuclear weapon capability, we can expect an Israeli attack that does not require U.S. permission, or even a warning.

Micah Zenko is a fellow in the Center for Preventive Action at the Council on Foreign Relation