Were that to happen, President Trump's actions in quitting the Iran accord would place a large share of the responsibility on the United States, increasing the likelihood that the U.S. would, in fact, support and reinforce Israel.

Saudi Arabia would be only too pleased to see Israel, with the backing of the U.S., strike Iran, as Iran well understands, especially if this were to disrupt Iran's ability to sell its petroleum.

War would also likely disrupt Iran's Hezbollah party in Lebanon and curtail Iran's movement toward the Mediterranean.

Russia, like Saudi Arabia, would welcome a spike in the price of oil, and the subsequent opportunity to expand its armament sales in the region. It will not be struck by either Israel or the United States, should the U.S. engage militarily, nor will it defend Iran.

Turkey would not be unhappy to see a regional rival struck and Iranian military efforts in Syria disrupted.

Thus, weighing the factors in balance, there is good reason for Iran to be open to European proposals to strengthen the provisions of the Joint Comprehensive Plan of Action, known as the Iran nuclear deal, and then try again to gain U.S. support.

Over many years the Iranian government has been hardline, determined, but, ultimately, rational. Only time will tell whether they respond now with outraged nationalism, and restart their nuclear program, or whether the cooler heads will prevail.

My own bet would be for a brief period - a few weeks - of calm while the Europeans try to salvage the deal by negotiating some marginal enhancements.

They might succeed if they can assuage Iranian pride by becoming the submissive demandeurs. But Iran has long anticipated strikes by Israel or the U.S., and has no doubt prepared assiduously. We should expect them to resist anything that seems to be "blackmail" by the Great Satan.

If this isn't resolved in a few weeks, Iran will likely move to complete its nuclear weapons program.

Should Israel and the U.S. strike, the hardliners in Iran will reckon that this will only increase popular support for the regime, while in Washington the unrealistic hopes that a few strikes will bring regime change will be replaced by the grim recognition that these strikes will lead the way to the third major U.S. military engagement in the Middle East begun without a clear strategy for successful conclusion.

The hardliners on both sides will have confirmed the enemy they have long decried. The world will see a destructive, futile, and useless war, likely to lead to yet another failed state.

Commentary by Retired General Wesley Clark, a former NATO Supreme Allied Commander and a Senior Fellow at the UCLA Burkle Center. Follow him on Twitter @ GeneralClark.

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