The Hill mentions a report from the Atlantic Council’s Iran Task Force:

The idea of establishing an American-staffed interests section in Iran was first considered by the George W. Bush administration and had the support of then Secretary of State Condoleezza Rice. In 2013, the Atlantic Council’s Iran Task Force, chaired by Ambassador Stuart Eizenstat, recommended the opening of an interests section in Tehran in a report titled Time to Move from Tactics to Strategy on IranAn interests section would be responsible for protecting America’s interests in Iran. It would not, however, be equivalent to the establishment of formal diplomatic relations with Iran.

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