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Tehran will be the top threat in 2012, former CIA Director Michael Hayden predicted Wednesday as Iran dominates foreign policy debate even while national security officials appeared to dismiss the Islamic Republic's latest threat to close the Strait of Hormuz.

"It is the single greatest destabilizing element right now with regards to global security," Hayden told Fox News, adding that the outlook is not encouraging.

"Of all the things that I left, when I was in government, the situation with Iran, and particularly their nuclear program has continued on a trajectory that gets darker with each passing day, week and month. They seem on this inexorable arc in the direction of a nuclear capability and there seems to be nothing that we or other like minded nations can do that will stop them."

Hayden who led the CIA from 2006 through 2009 and is now a principal with the Chertoff Group, which provides risk management and security services, said part of the problem is understanding the regime's intent.

"This government and its decision-making processes are incredibly opaque. And here we are, as a government trying to get them to change their mind, change their mind in a process that it is very difficult for us to identify where are the leverage points."

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On Monday, Iran's army chief warned against a U.S. carrier returning to the Strait of Hormuz, the critical passageway that the U.S. monitors as part of international agreement to keep the shipping lanes open. The USS John C. Stennis had vacated the area while Iran's navy conducted war games in the Persian Gulf over a 10-day period.

The U.S. dismissed the threat as the result of Iran's growing isolation and a lashing out at the international community. Hayden said the threat doesn't even make logical sense since he doubts Iran would have the ability to close the strategic waterway for any length of time in any case.

"I'm creative enough to imagine circumstances internal to Iran where some faction or another might believe it's to their internal advantage to take such a dramatic action. But externally it just doesn't make any sense," he said.

"Number one, they need the straits as much, perhaps more, than anyone else, the free flow of oil, otherwise their economy is more in the tank than it is today. Number two, does closing the straits make Iran more or less isolated? ... Does closing the straits make it more or less likely that someone will think it's a legitimate step to attack the nuclear facility at Natanz? I think it makes it more likely. So why would the Iranians do that?"

But Hayden warned that such a threat suggests that Tehran may commit an unforced error in the next year, which could have profound consequences.

"Who is likely to go dramatic in 2012? It's not us, I don't think it's the Israelis. I think it's the Iranians. And I think it's out of desperation and miscalculation. The isolation that they are undergoing right now is very severe. Their currency is dropped about one-third of its value in the past few weeks. And now with the imposition of sanctions against the Iranian national bank and the impact that will have on the oil industry, you are seeing great stresses within the Iranian leadership structure."

The alleged Iranian-backed assassination plot to target the Saudi envoy to Washington DC in November 2011 underscores the possibility of Iranian missteps.

"A country that's willing to try to kill Adel al-Jubeir, the Saudi ambassador, at a Georgetown restaurant, through a Mexican drug cartel, is probably capable of a lot of things," he said.

Hayden, who in addition to being CIA chief also led the National Security Agency, said there is significant common ground between the Bush and Obama White House on Iran strategy.

"This is not an issue that we left the administration with easy answers, the current administration, with easy answers. We (the previous administration) struggled with this as well. There are no really good options. We have tools, we talk about the continuity between the two administrations when it comes to the war on terror, it's actually been a fair amount of continuity between the two administrations when it comes to Iran as well."

The first intelligence officer to reach the rank of four stars in the Air Force, Hayden added that the Bush administration wrestled with the same issues the current administration has to cope with, in part because, efforts to engage Iran have not gone according to plan.

"We had that interlude where we tried to engage Iran, and that of course did not end well. But by and large the administration has depended upon an international coalition. The administration has depended upon economic sanctions. The administration has depended upon attempts to isolate Iran, internationally. All of those are carrying forward policies developed during the previous administration. It's just a hard problem."

As for the effectiveness of a covert campaign in Iran, which has reportedly targeted nuclear scientists and nuclear facilities, Hayden would not comment directly but said from what he's read in the newspaper, "someone has a very aggressive covert action campaign apparently, against the Iranian program."

"And it appears to be setting the program back," he added. "The Iranians always made claims for their program, that the program was far more advanced than, than we knew it to be. I think we still see that today."

Fox News chief intelligence correspondent Catherine Herridge's bestselling book "The Next Wave: On the Hunt for al Qaeda's American Recruits," published by Crown, draws on her reporting for Fox News into al Qaeda 2.0. It investigates the new face of terrorism.