The US foreign policy in the Middle East needs a state like Iran, to justify its presence. Imagine a peaceful Middle East without Iran, Hizbullah, and without US military presence or military spending!!!!, where oil prices would be low and stable. Can you imagine the adverse economic consequences for that. Many US corporate which is mostly owned by the US warlords would collapse. Conclusion: the Iranian nuclear program will continue, and Iran influence will grow stronger, until the world cannot tolerate it. And then the US will look for another source of profit/trouble.
from the article: Russia says Iran's nuclear power plant fully operational