To be sure, the United States and Iran remain divided on a    number of major political issuesincluding Iran's support for    Syria's leadership, and perhaps especially its refusal to    recognize the state of Israel. Iran has also directed extremely    threatening language toward Israel, a critical U.S. ally.  
    Aside from Israel, U.S. allies Saudi Arabia and the United Arab Emirates would become concerned    by renewed relations between the United States and Iran. Saudi    Arabia has remained the top U.S. ally in the region (besides    Israel) because it has provided abundant oil and cooperated    with American military activities in the region, Bremmer said.    But that relationship may be no more of a natural fit than a    relationship with Iran.  
    "These are strategic allies of convenience, but there's not a    lot that really binds them together," Bremmer said.  
    Read MoreWithout a deal, Iran's economy    to be on 'its knees'  
    American and European financial institutions and companies    would be hesitant to do business in Iran in a post-sanctions    world, Clawson said.  
    Corruption remains a serious problem, and foreign businesses    see the issue as having become even more thoroughly entrenched    in recent years as Iran has had to devise ways to evade    sanctions, Clawson said. The Revolutionary Guards, a    politically powerful branch of the Iranian military, has a    tendency to muscle into markets after merchants make them    profitable, making it difficult to determine which sectors are    truly private, he added.  
    Clawson also anticipates banks will be wary of running afoul of    regulators following Commerzbank's anticipated $1 billion settlement    with the U.S. Justice Department on charges that it violated    Iranian sanctions and money laundering laws. Standard Chartered paid $327 million to settle    similar claims two years ago.  
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    Ultimately, the United States has a broader incentive for    rapprochement with Tehran. Iran has the potential to present a    model for what world trade and globalization can bring to the    Middle East, said Salehi-Isfahani. By playing the development    game, Iran could influence its neighbors to do the same.  
    "This idea that you behave yourself, you have elections, you    elect moderate leaders, you build your roads and schools, and    you succeed, that's a lesson that Americans are trying to sell    to the world," he said. "If Americans have any role in making    that happen [in Iran], that will be the most stabilizing    influence in the Middle East of anything I can see the    Americans doing."  
More here:
US and Iran could become, well, BFFs...really