PBW and Massi you're both right to some extent... The only thing that you need to realize is the US does not want to control the oil in the ME - at least not any more. They just want to control the flow of oil (and other hydrocarbons) out of the middle east and North Africa to keep the price of oil at a certain threshold. The best way to do that is through a controlled creation, escalation and de-escalation of conflicts in the region. The US is now a net exporter of oil by some accounts and within the next few years by all other accounts (also a net exporter of energy now).
They need oil and other hydrocarbons to be at a certain price to make this a profitable venture for that industry (with serious lobbying power), in lieu of their high extraction costs. It's also a way of keeping the Chinese, Indians and Turks in check since they are net importers. Canada and other western producers of oil are all in the same shoes. If oil drops to $70 for example, Canada's economy will go to shits - China's economy will prosper on the other hand. That's why you see the Chinese opposing action in Syria and specifically mentioning the price of oil.
And of course the Saudis and other Arab nations are going along for the ride. They have the cheapest extraction costs in the world. The higher the price of hydro carbons, the better for them. And what better way to do that than to take Libyan, Syrian or Iranian oil (i.e. all the oil being sold by bad guys) off the markets - in a controlled manner, just to keep the supplies in check with demand to maintain that threshold. Unfortunately, we have a stupid government who finally caught on to this scheme just a few months ago. That's why you see Zanganeh coming out and saying that he wants to increase oil production - only to remember that we can't even sell the oil that we're extracting! And that's why you see the Obama administration specifically bringing up the threat of force against Syria, despite the deal reached last week, as soon as oil starts heading south!
The Americans are not going to give up this perfect set up they have going. Unless the political benefit of a potential deal with Iran is much bigger to Obama and the Democrats than the benefit to their supporters in the energy industry, there's absolutely no reason for them to mess up a good thing. Sure, if Obama comes out of this with a deal under which Iran halts all enrichment, allows unconditional access for IAEA inspectors to ALL sites and dismantles Fordow and a couple of other sites, and a gradual lifting of sanctions subject to verification of compliance with the first few items, where he can look like a total hero, we can expect a deal. But I'd say that's about the only scenario under which a deal can happen - the IR begging on its knees, accepting total defeat and still being out of oil markets for the next 6 months to a year. Even if Rohani was authorized to accept that deal, I can't see it going down in Iran with the hardliners - that would be the end of IR much sooner than the alternative!