With Iran now largely capable of developing a nuclear weapon, the goal of US policy should be to dissuade it from taking the fateful, next step of making a weapon, urged a study released Tuesday.

And if it fails, the United States should have a strategy worked out to deter a nuclear armed Iran, said the study by the RAND Corporation, which was sponsored by the US Air Force.

"There is still time to dissuade Iran from weaponizing its program," said Alireza Nader, one of the authors of the report, "Iran's Nuclear Future: Critical US Policy Choices."

The report reflects a shift in US policy circles over how to deal with Iran as mounting international sanctions on the regime have failed to reverse the direction of its nuclear program.

Calls for military strikes to take out Iran's nuclear capabilities have faded as the implications for the region have sunk in. Even in Israel, which has long viewed Tehran as an existential threat, comments by a former intelligence chief have exposed doubts about how to deal with the threat.

Further complicating the policy choices facing the United States is the Arab Spring, which may usher in regimes who prefer a softer approach toward Iran in countries that currently host US forces.

The RAND report said Iran already has largely acquired the materials, equipment and technology needed to develop a nuclear weapon.

"International efforts to control exports and interdict trade can now only hope to slow Iran's progress and possibly deny it the specific technologies needed, for example, for nuclear warhead miniaturization and for mating a warhead on a missile.

"Thus, the Iranian action that the United States will wish to dissuade in the future will be nuclear weaponization," it said.

The report's authors argue that there are factions and personalities within Iran with differing views over whether or not to 'weaponize' the country's nuclear program, and US and international pressure can still affect the outcome of the debate.

"We see such a goal as facing really serious obstacles but believe it is too soon to give up trying," said Lynn Davis, a former under secretary of state for arms control and international security who led the study.

"It is still possible in our view to influence the outcome of the internal political debate in Iran," she said.

"The bottom line from our point of view is -- shared by the intelligence community -- that Iran has yet to make a decision with respect to its nuclear program," she said in a conference call.

Echoing the report, she emphasized the need for an integrated US strategy that anticipates the future evolution of the Iranian nuclear program, rather than policies "we see today arising primarily from the art of the possible."

While it makes no specific policy recommendations, the report analyzes the pros and cons of various strategies to dissuade Iran from "weaponizing," and how they are likely to suit US partners in the region.

These include various forms of sanctions and military steps that could be taken to show Iran that it will pay a price and can gain nothing from such a fateful step.

But it also includes a chapter on deterring Iran if it does acquire nuclear weapons, either declaring itself a nuclear state or maintaining an ambiguous posture by not admitting to having the weapons.

Among the possible military steps suggested in the report were exercises and temporary deployments of nuclear capable bombers in the region, and committing nuclear capable assets for planning purposes to respond to Iran's use of nuclear weapons.

To deny Iran any gain from developing nuclear weapons, the United States could seek capabilities to seek, locate and destroy Iranian weapons before they are launched, the report said.

The report also had some advice for the US Air Force: design exercises that show it can put Iran's nuclear capabilities at risk, but be sensitive to how such shows of force might impact the internal debate in Iran.

"Because there is the prospect that Iran could develop nuclear weapons, either a virtual capability or a declared capability, it is now time for the United States and others to begin to think about how deterrence might be achieved, again influencing Iran in the potential use of its nuclear weapons," Davis said.

"I would suspect there is some planning going on, but our value here is helping planners not only here in the United States but around the world to think about the future," she said.